Fornax Galaxy Research Articles

A Search for Globular Clusters in the Surroundings of Dwarf Galaxies in Fornax: Intracluster Globulars?

We present the results of a search for globular clusters in the surroundings of 15 low surface brightness dwarf galaxies in the Fornax cluster, on CCD images in the C and T1 bands. Globular cluster candidates show a clear bimodal color distribution. Their surface density distribution shows no concentration towards the respective dwarf galaxies but it does show concentration towards the center of the Fornax cluster. We suggest that the potential globular clusters might not be bound to the dwarf galaxies, but might instead belong to the intra-cluster medium.

The neutral hydrogen content of Fornax cluster galaxies

We present a new set of deep H I observations of member galaxies of the Fornax cluster. We detected 35 cluster galaxies in H I. The resulting sample, the most comprehensive to date, is used to investigate the distribution of neutral hydrogen in the cluster galaxies. We compare the H I content of the detected cluster galaxies with that of field galaxies by measuring H I mass-to-light ratios and the H I deficiency parameter of Solanes et al. (1996). The mean H I mass-to-light ratio of the cluster galaxies is 0.68 +/- 0.15, significantly lower than for a sample of H I-selected field galaxies (1.15 +/- 0.10), although not as low as in the Virgo cluster (0.45 +/- 0.03). In addition, the H I content of two cluster galaxies (NGC1316C and NGC1326B) appears to have been affected by interactions. The mean H I deficiency for the cluster is 0.38 +/- 0.09 (for galaxy types T = 1-6), significantly greater than for the field sample (0.05 +/- 0.03). Both these tests show that Fornax cluster galaxies are H I-deficient compared to field galaxies. The kinematics of the cluster galaxies suggests that the H I deficiency may be caused by ram-pressure stripping of galaxies on orbits that pass close to the cluster core. We also derive the most complete B-band Tully-Fisher relation of inclined spiral galaxies in Fornax. A subcluster in the South-West of the main cluster contributes considerably to the scatter. The scatter for galaxies in the main cluster alone is 0.50 mag, which is slightly larger than the intrinsic scatter of 0.4 mag. We use the Tully-Fisher relation to derive a distance modulus of Fornax relative to the Virgo cluster of -0.38 +/- 0.14 mag. The galaxies in the subcluster are (1.0 +/- 0.5) mag brighter than the galaxies of the main cluster, indicating that they are situated in the foreground. With their mean velocity 95 km s(-1) higher than that of the main cluster we conclude that the subcluster is falling into the main Fornax cluster.

Surface Brightness Fluctuations of Fornax Cluster Galaxies: Calibration of Infrared Surface Brightness Fluctuations and Evidence for Recent Star Formation

We have measured KS-band (2.0-2.3 μm) surface brightness fluctuations (SBFs) of 19 early-type galaxies in the Fornax Cluster. Fornax is ideally suited both for calibrating SBFs as distance indicators and for using SBFs to probe the unresolved stellar content of early-type galaxies. Combining our results with published data for other nearby clusters, we calibrate KS-band SBFs using Hubble Space Telescope (HST) Cepheid cluster distances and I-band SBF distances to individual galaxies. With the latter, the resulting calibration is valid for 1.05 < (V-Ic)0 < 1.25 and not including any systematic errors in the HST Cepheid distance scale. The fit accounts for the covariance between V-Ic and KS when calibrated in this fashion. The intrinsic cosmic scatter of KS appears to be larger than that of I-band SBFs. S0 galaxies may follow a different relation, although the data are inconclusive. The discovery of correlation between KS-band fluctuation magnitudes and colors with V-Ic is a new clue into the star formation histories of early-type galaxies. This relation naturally accounts for galaxies previously claimed to have anomalously bright K-band SBFs, namely, M32 and NGC 4489. Models indicate that the stellar populations dominating the SBF signal have a significant range in age; some scatter in metallicity may also be present. The youngest ages imply some galaxies have very luminous giant branches, akin to those in intermediate-age (few Gyr) Magellanic Cloud clusters. The inferred metallicities are roughly solar, although this depends on the choice of theoretical models. A few Fornax galaxies have unusually bright KS-band SBFs, perhaps originating from a high-metallicity burst of star formation in the last few Gyr. The increased spread and brightening of the KS-band SBFs with bluer V-Ic suggest that the lower mass cluster galaxies (0.1L*) may have had more extended and more heterogeneous star formation histories than those of the more massive galaxies.

X-Ray Measurements of the Field and Particle Energy Distributions in the West Lobe of the Radio Galaxy NGC 1316 (Fornax A)

A follow-up X-ray study was made of the west lobe of the radio galaxy Fornax A (NGC 1316) that was based on new ASCA observations made in 1997 for 98 ks and that incorporated the previous observation in 1994 for 39 ks. The 0.7-10 keV spectrum of the emission can be described by a power law with an energy index of 0.74 ± 0.10, which agrees with the synchrotron radio index of 0.9 ± 0.2. Therefore, the X-rays are reconfirmed to arise via the inverse Compton scattering of the cosmic microwave photons, as Kaneda et al. and Feigelson et al. concluded. The surface brightness of the inverse Compton X-rays exhibits a relatively flat distribution over the west lobe, indicative of an approximately spherical emissivity distribution with a radius of ~11' (75 kpc). In contrast, the 1.4 GHz radio image by Ekers et al. exhibits a rim-brightened surface brightness, consistent with a shell-like emissivity distribution whose inner and outer boundaries are 4' and 11', respectively. These morphological differences between radio and X-rays suggest that the relativistic electrons are distributed homogeneously over the lobe volume, whereas the magnetic field is amplified toward the lobe rim region.

Circumnuclear Star Formation in the Early-Type Resonance Ring Barred Spiral Galaxy NGC 1326

We present multiband WFPC2 images of the nuclear ring of NGC 1326, an early-type southern barred spiral in the nearby Fornax galaxy cluster. The ring is a typical example of a 1 kpc–sized star-forming ring located in the region of the inner Lindblad resonances with the weak primary bar. The images reveal nearly 1000 point sources in and around the ring. Those sources brighter than MV = -9 are probably massive young clusters, while the fainter sources may include a mix of extremely luminous stars and fainter clusters. From an analysis of reddening-free parameters and two-color plots, we find evidence for a spread in ages of ring clusters, from less than 5 Myr to at least 200 Myr. The older still lie within the nuclear ring, with no evidence of migration of the ring being found over this time period. The luminosity function reveals no having an (uncorrected) absolute magnitude MV brighter than -11, and even after correction for extinction the most luminous cluster identified has only M = -12.6. The ring seems to lack the super–star clusters (SSCs) seen in starburst systems and in other nuclear rings, and the analysis suggests that SSCs are not a universal property of these rings. Complex dust structure is found inside the ring, south of the nucleus, and extinction is especially severe on the west side of the ring. An Hα image reveals hundreds of H II regions and emission complexes in the nuclear ring, but there is little correlation between these H II regions and the observed continuum sources, most likely owing to reddening and age differences in the ring.

The NGC 1399 Globular Cluster System: Washington Photometry Revisited

A new analysis and discussion of Washington CCD photometry for some 500 globular cluster candidates associated with the Fornax cluster cD galaxy NGC 1399 are presented. The image handling in this work includes improved methods for the removal of both the galaxy halo and fringing effects over that employed in a previous work of ours. The analysis of the globular cluster candidates inside an annular region between 05 and 4' from the galaxy center using two-color diagrams shows a clear bimodal distribution for objects fainter than T1 = 21.0 (V ≈ 21.5). The modal colors of the globular clusters belonging to the red population are coincident, within the measuring uncertainties, with those of the galaxy halo. In turn, the average integrated colors of the blue population are comparable to those of the bluest non–star-forming low surface brightness galaxies in Fornax. Red clusters appear more centrally concentrated than the blue clusters. A new determination of the integrated luminosity function turnover (T1 = 23.24) leads to a distance modulus for NGC 1399 of V0 - MV = 31.02 ± 0.2. The total number of globular clusters, combined with our preliminary photometry of the galaxy halo, leads to an overall specific frequency SN = 5.6 ± 1.0, which is considerably lower than previous estimates available in the literature. We note that these last values have been based on an extrapolation of aperture photometry of the inner regions of the galaxy.

Placing the Fornax and Sagittarius Dwarf Spheroidal Globular Clusters in the Horizontal-Branch Type versus Metallicity Diagram

We plot the globular clusters of the Fornax galaxy and those associated with the Sagittarius dwarf spheroidal galaxy in the horizontal-branch type versus metallicity diagram. The horizontal-branch types for the Fornax clusters include corrections for red horizontal-branch stars from the field and are based on our recent work and new results in the literature. Fornax globular clusters continue to stand out as having red horizontal branches for their low ([Fe/H] ~ -2) metallicities, with no counterparts in either the outer Galactic halo or the Magellanic Clouds. The clusters associated with Sagittarius lie to the blue of the Fornax clusters, except for the metal-rich cluster Ter 7. Although the metallicities of the three metal-poor Sagittarius globular clusters are similar to those of the Fornax clusters, their horizontal branches are bluer and they lie in a region also populated by the old LMC and old halo clusters. Neither cluster system resembles the younger Galactic halo globular clusters, often suggested to have been accreted from disrupted dwarf spheroidal galaxies. Except for Ter 7, both the Fornax and Sagittarius globular clusters are metal-poor compared with their Galactic counterparts of the same horizontal-branch type. We find no correlation between HB type and other cluster properties such as central concentration, luminosity, central surface brightness, and estimated collision rate.

Homogeneous Photometry for Star Clusters and Resolved Galaxies. I. A Survey of Bright Stars in the Fornax Dwarf Spheroidal Galaxy

ABSTRACTWe present accurate photometry on the Johnson B, Kron‐Cousins R photometric system for approximately 100,000 stars in a 1 / 3 deg2 field centered on the dwarf spheroidal galaxy in Fornax. We identify numerous probable short‐period variable stars, blue stars that appear to be the main sequence of a small population with an age of order 108 yr, and two distinct types of luminous red star: an extended sequence of primarily carbon stars and a clump of mostly M giants slightly more luminous than the giant‐branch tip. The spatial distribution of each of these subpopulations within the Fornax dwarf galaxy is considered.

Evidence for a Dramatic Activity Decline in the Nucleus of the Radio Galaxy Fornax A

Fornax A (NGC 1316) is a radio galaxy with prototypical double lobes. Feigelson et al. (1995 ApJ 449, L149) and Kaneda et al. (1995 ApJ 454, L13) detected inverse Compton X-rays for the first time from its radio lobes, and unambiguously derived the lobe magnetic field intensity of 2-4 μG. Accordingly, the radio-emitting electrons in the lobes are inferred to have a Lorentz factor of 104, and hence a synchrotron life time of ~108 yr. This means that Fornax A was highly active at least 108 years ago.

X‐Ray Emission from the Fornax Cluster

We have analyzed the ROSAT PSPC observations of the central region of the Fornax cluster, a relatively poor group of galaxies at a distance of about 24 Mpc. The brightest X-ray and optical galaxy in the group is NGC 1399, an E1 galaxy located near the center of the Fornax cluster. We characterize the hot gas around the galaxy, derived from a 2' to 18' annulus around NGC 1399, as having a mean temperature of 1.30 ± 0.05 keV and a heavy element abundance of 0.6 ± 0.1 with respect to solar abundance (Fe/H = 4.68 × 10-5 by number). Spatially resolved spectral data provide both gas temperature and gas abundance profiles extending to 125 kpc (18') from the galaxy. The temperature distribution, combined with the X-ray surface brightness profile, yields an accurate determination of the gravitating mass within 125 kpc, which falls in the range (4.3-8.1) × 1012 M☉ (95% confidence range, including systematic uncertainties). If we include the extended optical halo around NGC 1399, the mass-to-light ratio increases with radius from 33 ± 8 M☉/L☉ at 18 kpc to 70 ± 22 M☉/L☉ at 110 kpc. We compare the heavy element abundance distribution measured around NGC 1399 with that measured around the Virgo galaxy NGC 4472, as well as to models for hot coronae. We find that the abundance distribution is in good agreement with that previously measured for NGC 4472 by Forman et al. in 1993. For both galaxies, the observed abundance profiles require both a weak evolution of the type Ia supernova rate with time and a present epoch rate which agrees with that of Cappellaro et al. We compare mass measurements in NGC 1399 to those for M87. The similarity of the optical masses in these systems and their differences in gas masses and gravitating masses lead us to suggest that the optical galaxies formed at an early stage when the central potentials of these two systems were similar. Subsequent infall of gas and dark matter into the larger, deeper Virgo potential resulted in the greater mass of the Virgo cluster compared to Fornax. We also report on X-ray properties of thirteen other Fornax galaxies. Eight of these were detected in ROSAT images with luminosities in the 0.2 to 2 keV energy band from 1 × 1039 to 1.6 × 1041 ergs s-1. Five galaxies were sufficiently bright to permit spectral analyses and all but one (NGC 1380) had spectra consistent with thermal emission. Two (NGC 1404 and NGC 1387) of the four galaxies with well-constrained spectral parameters have hot coronae with characteristic gas temperatures of about 0.5 keV and iron abundances less than that found around NGC 1399 and other bright ellipticals. To maintain these hot coronae, the absolute magnitudes of these galaxies must be brighter than -19. Thus the distance to Fornax must be at least 18 Mpc, and, if there are no large peculiar velocities, the Hubble constant should be less than 75 km s-1 Mpc-1. Since these galaxies are all members of Fornax, distance uncertainties do not affect the relationship between their optical magnitude and X-ray luminosity. Analysis of the Fornax galaxies supports the contention that the scatter in the X-ray and optical relationship is intrinsic and does not arise solely from distance uncertainties. For the elliptical galaxy NGC 1404, the X-ray images show that the hot corona is distorted and likely is being stripped, indicating infall of the galaxy toward NGC 1399 and the cluster center.

Intergalactic stars in the Fornax cluster

We have identified ten candidate intergalactic planetary nebulae in the Fornax galaxy cluster. These objects were found during observations in 1992 and 1993 in three fields chosen well away from any Fornax galaxy at 15 arcmin, 30 arcmin, and 45 arcmin from the centre of Fornax. We used the usual method of blinking images taken in a narrow OIII filter, with images taken in an adjacent broad filter. The measured fluxes in the narrow, broad, and I bands are consistent with these unresolved objects being planetary nebulae immersed in an intergalactic population of stars. Such a population is expected to arise as a consequence of tidal encounters between galaxies, and our findings strengthen the case for the existence of such tidal debris. The confirmation of some or all of these ten candidates as planetary nebulae would imply that intergalactic stars constitute a substantial fraction of all the stars in Fornax, up to an estimated 40 per cent. Intergalactic planetary nebulae could prove useful in probing the underlying cluster potential, since they would be far more abundant than galaxies. We discuss possible contamination of the sample by emission-line galaxies, but conclude that planetary nebulae is the most likely identification for the detected objects. keywords: intergalactic medium-- galaxies: interactions -- planetary nebulae: general -- clusters: individual: Fornax

UBVRI PHOTOMETRY OF SPIRAL GALAXIES IN THE VIRGO AND FORNAX CLUSTERS

ABSTRACT In this study multi-aperture photo electric photometry in the five passbands UBVRI for 171 and 46 galaxies in the Virgo and Fornax clusters, respectively, are presented. New radial velocities and H I profiles for 17 galaxies in Fornax have been obtained. Total magnitudes and colours are derived for around 800 individual measurements using standard growth curves in B, U-B and B-V. Total colours V-R and R-I are derived from a set of synthetic colour growth curves. The resulting total B magnitudes have an internal error of 0.09 mag, the U-B colours have an internal error of 0.03 mag, and in B-V V-R and R-I the error is 0.02 mag. The derived magnitudes of a nearly complete sample (~90%) of all Virgo and Fornax spirals with i >/= 45 degrees (as listed in the Virgo and Fornax cluster catalogues) lend themselves for a detailed study of the luminosity-line width relation (Tully-Fisher relation) in UBVRI. In particular the effects of different parameter sets (line widths, axial ratios, morphological types) and corrections on the luminosity-lkine width relation are investigated. Furthermore, the dependence on morphological galaxy type is examined, new internal absorption corrections are derived and the accuracy of the luminosity-line width method in different passbands is studied. The data are used to determine a distance of the spiral galaxies of the Fornax cluster relative to the Virgo spirals. The results are as follows: The slope of the luminosity-line width relation in B is -6.50 ± 0.36 and depends on the line width correction. Differences of up to 0.2 mag in the intercept of each cluster are found when using different input parameter; changes due to different corrections apply to both clusters simultaneously, and have little effect on the relative distance. Subsamples as to inclination or galaxy type affect the relative distance only marginally, while a restriction in apparent magnitude results in a change of the slope and the intercept of each cluster and of the relative distance. A limitation in line width affects Fornax more than Virgo, because the scatter in the luminosity-line width relation of the Fornax cluster changes strongly with line widths (or magnitude). The luminosity-line width relation s in other passbands show the same scatter for Virgo (about 0.64 mag); in Fornax the scatter varies with wavelength and is largest in the I-band. The slope is dependent on wavelength and approaches an asymptotic value of about -8.5 at long wavelengths. The mean relative distance modulus over all passbands is mF - mV = -0.40 ± 0.10 mag. The variation of the inclination dependent part of the internal absorption with wavelength is investigated. The colours show a dependence on axial ratio only for Sb to Scd galaxies. The resulting internal absorption with respect to the RC3 B-band absorption for these galaxy types is 116% in the U-band, 82% in V, 74% in R and 63% in I. Furthermore, a new absorption law of AB = 1.7 log R was found for Sb to Scd galaxies (as compared with the RC3 law of AB = 1.47 log R), though the present sample is too small for the result to be reliable. The potential of a luminosity-colour relation is inspected. However, error and scatter are much higher than in the luminosity-line width relation. The resulting relative distance of Fornax and Virgo is consistent within the errors with the distance found using the luminosity-line width relation. The spiral galaxies of the Fornax cluster are found to be closer than the Virgo spirals by 0.40 mag. The resulting peculiar velocity of Fornax relative to Virgo lies between 150 km s-1 and 300 km s-1, depending on the virgocentric infall model, and points away from the Local Group. The division of Virgo into subclusters and the effect of H I stripping are discussed.

Cooling-Flow Models of the X-Ray Emission and Temperature Profiles of Elliptical Galaxies

We compare the results of a spherical, steady-state cooling-flow model with gas loss with the observed X-ray emission profiles and temperatures for five bright elliptical galaxies in Virgo and Fornax. We adopt a “thermal-instability” mass-loss prescription (following Sarazin &amp; Ashe 1989) and refer to galaxy models constrained by radially extended stellar dynamical data (Saglia et al. 1992). Our cooling-flow models are specified by three free parameters: the mass accretion rate and the pressure pext at some external radius rext, and a dimensionless constant q, which regulates the mass deposition rate along the flow. We find that models with confining pressures of pext ≃ 4 ÷ 14 × 103K cm–3 and significant accretion rates of external material, up to 4M⊙/yr, provide emission and temperature profiles in good agreement with present-day data. The trend shown in the right frame of the lower panel in the Figure suggests a possible correlation between LX/LB and the iron abundance in the gas inside ellipticals. A full account of this work, together with all the relevant references, is given in Bertin &amp; Toniazzo (1995); here below, we add a comparison of the models with some recent ASCA data (Loewenstein et al. 1994; Mushotzky et al. 1994).This work was partially supported by ASI (under contract 94RS94-202/3 FAE) of Italy.

Detection of Inverse-Compton X-Rays from Lobes of the Radio Galaxy Fornax A

Extended X-ray emission was detected with ASCA from the synchrotron double lobes of the radio galaxy Fornax A. This is thought to be the same emission as was detected with ROSAT. The excess X-rays exhibit very hard spectra, described by a power law of energy index 1.2 ± 0.5. Since this index is consistent with the synchrotron radio index of 0.9 ± 0.2, the X-rays are thought to arise when the radio-emitting relativistic electrons make inverse-Compton scattering off the cosmic microwave photons. Comparison of the X-ray and radio fluxes yields the lobe magnetic field intensity of 2-4 μG. The relativistic electrons in the lobes are inferred to have an energy density close to that of the magnetic fields.

Cooling Flow Models of the X-Ray Emission and Temperature Profiles for a Sample of Elliptical Galaxies

A simple spherically-symmetric, steady-state, cooling-flow description with gas loss (following Sarazin \& Ashe 1989), within galaxy models constrained by radially extended stellar dynamical data, is shown to provide generally reasonable fits to the existing data on X-ray emission profiles and temperatures for a set of bright elliptical galaxies in Virgo and Fornax. Three free parameters are needed to specify the model: the external mass flux, the external pressure, and a dimensionless factor, which regulates the mass deposition rate along the flow. Three different assumptions on the supernova rate have been considered. A moderate value for the supernova rate in elliptical galaxies is found to be preferred. Confining pressures of $p_{ext}\sim4\div15\times10^3\kelvin$ cm$^{-3}$ and significant accretion rates of external material, up to $4\msolar/\yr$, are suggested by our models. A possible correlation between $L_X/L_B$ and the iron abundance in the gas inside ellipticals is pointed out.

Discovery of Inverse-Compton X-Rays in Radio Lobes

Inverse-Compton (IC) scattering of cosmic microwave background photons into the X-ray band by relativistic electrons in diffuse radio lobes is an obligatory process. We present the strongest evidence to date for the detection of these IC X-rays. They appear in a deep image of the nearby radio galaxy Fornax A (=NGC 1316) obtained with the Position Sensitive Proportional Counter on board the ROSAT satellite. The spatial correspondence of the X-ray and radio emission is excellent. The absence of Faraday depolarization in the lobes argues strongly against the possibility that the X-rays are due to an entrained thermal plasma. The detected level of X-rays is somewhat higher than, but consistent with, that expected from the assumption of equipartition between magnetic fields and relativistic electrons in the lobes. This observation provides the first direct estimate of the magnetic field of a radio lobe, BIC 2-3 μG, indicating that the integrated energy output of this active galactic nucleus is near the minimum energy level.

Extragalactic Ionized Hydrogen in the Fornax Cluster

The radio galaxy Fornax A is well known for its giant radio lobes which extend almost a degree (~300 kpc) across the sky. Fomalont et al. have shown that these lobes are linearly polarized on the largest scales, although the western lobe is highly depolarized in discrete, resolved regions. The depolarized regions indicate the presence of ionized gas (Faraday screen) along the line of sight to the western lobe. We have now detected the warm gas at H? using a Fabry-Perot interferometer in a way that allows us to reach very low surface brightness levels (<10-19 erg cm-2 s-1 arcsec-2). The radial velocity of the ionized gas (1610 km s-1) places it in the Fornax cluster at a projected radius of 1.0 Mpc. The gas is spread over a region 10 kpc in diameter and has an ionized mass of 6 × 107 f-0.5 M? (where f is the volume filling factor). For the inferred column density of electrons (?2.6 × 1020 f-0.5 cm-2) and in light of the H I upper limits (<4 × 1019 cm-2), the cloud has to be mostly ionized. Possible sources of ionization are large-scale shocks or a putative hot component which confines the radio lobes. The high line-of-sight magnetic field strength (B? ? 0.3-1.3 ?G) deduced from the rotation measure (?20 rad m-2) and energy equipartition suggests that the cloud may have undergone significant turbulent heating from secondary shocks. The predicted bounds on the fraction of neutral material (10-6-10-1) indicates that this may be the first example of a spatially resolved, extragalactic ionized cloud. Such objects are thought to be responsible for some of the Ly? absorption lines observed in the spectra of quasars.

The giant branch of the Fornax dwarf spheroidal galaxy

A color-magnitude diagram for a large sample of stars in the Fornax dwarf spheroidal galaxy has been obtained from BV electronographic observations. These reach to the level of the horizontal branch, below V = 21 mag. The area of investigation is located ~ 18 arcmin away in a southwest direction from the center of the Fornax galaxy. The wide field of the McMullan camera enabled some 1300 stars to be measured and made possible an analysis of structure in the giant branch. The standard deviation of the intrinsic width of the giant branch is ~0.14 mag in (B-V) color at a given luminosity, which yields a standard deviation of 0.3 in Fe/H, if a spread in metallicity alone is responsible for the intrinsic width. Otherwise a combination of both variation in age from 3 to 17 billion yr and a spread in metallicity equivalent to a standard deviation of 0.27 in Fe/H can account for the intrinsic width of the giant branch. A comparison with galactic globular clusters as well as theoretical isochrones suggests a mean value of [Fe/H] = -1.5 ± 0.1 for the Fornax giant branch stars.

The surface brightness of 1550 galaxies in Fornax: automated galaxy surface photometry - II

The surface brightness of 1550 galaxies in Fornax: automated galaxy surface photometry - II

Dwarf elliptical galaxies in the Fornax cluster. I - A catalog and luminosity function

view Abstract Citations (52) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Dwarf Elliptical Galaxies in the Fornax Cluster. I. A Catalogue and Luminosity Function Caldwell, Nelson Abstract A catalog of 145 dwarf elliptical galaxies in the Fornax cluster is presented which is believed to be complete to a blue magnitude of 18.5, although galaxies with luminosities 2 mag below that limit have been found. The dwarf galaxies are less centrally concentrated in the cluster than are the bright galaxies. The ratio of the number of dwarf elliptical to elliptical galaxies is significantly smaller than the ratio found in the Virgo cluster. Interestingly, the ratio of dwarf ellipticals to actively star-forming galaxies (spirals and irregulars) in Fornax is similar to that in Virgo. The form of the velocity distribution of the dE's and star-forming galaxies is non-Gaussian, whereas that for the E/S0 galaxies is Gaussian. The velocity dispersion of the E/S0 group is low, at 300 km s-1. Publication: The Astronomical Journal Pub Date: November 1987 DOI: 10.1086/114549 Bibcode: 1987AJ.....94.1116C Keywords: Astronomical Catalogs; Dwarf Galaxies; Elliptical Galaxies; Galactic Clusters; Luminosity; Comparison; Velocity; Virgo Galactic Cluster; Astrophysics; GALAXIES: GENERAL; GALAXIES: CLUSTERING full text sources ADS | data products NED (211) SIMBAD (144) Related Materials (1) Part 2: 1987AJ.....94.1126C