Fornax Dwarf Elliptical Galaxies Research Articles

The H i content of Fornax dwarf elliptical galaxies: FCC032 and FCC336

We present H I21-cm line observations, obtained with the Australia Telescope Compact Array, of two dwarf elliptical galaxies (dEs) in the Fomax cluster: FCC032 and FCC336. The optical positions and velocities of these galaxies place them well within the Fornax cluster. FCC032 was detected at the 3σ significance level with a total HI flux density of 0.66 ± 0.22 Jy km s -1 or an HI mass of 5.0 ± 1.7 x 10 7 h -2 75 M ○. . Based on our deep Ha + [N II] narrow-band images, obtained with FORS2 mounted on the Very Large Telescope, this dE was already known to contain 600 -1800 h -2 75 M ○. of ionized hydrogen (depending on the relative strengths of the Hα and [N II] emission lines). Hence, this is the first study of the complex, multiphase interstellar medium of a dE outside the Local Group. FCC336 was detected at the same significance level: 0.37 ± 0.10 Jy km s -1 or a total H I mass of 2.8 ± 0.7 x 10 7 h -2 75 M ○. . Using a compilation of H I data of dwarf galaxies, we find that the observed high HI mass boundary of the distribution of dwarf irregulars, blue compact dwarfs and dwarf ellipticals in a log L B versus log M HI diagram is in good agreement with a simple chemical evolution model with continuous star formation. The existence of many gas-poor dEs (undetected at 21 cm) suggests that the environment (or, more particularly, a galaxy's orbit within a cluster) also plays a crucial role in determining the amount of gas in present-day dEs; for example, FCC032 and FCC336 are located in the sparsely populated outskirts of the Fomax cluster. This is in agreement with H I surveys of dEs in the Virgo cluster, and an Ha survey of the Fornax cluster, which also tend to place gas-rich dwarf galaxies in the cluster periphery.

Embedded disks in Fornax dwarf elliptical galaxies

We present photometric and kinematic evidence for the presence of stellar disks, seen practically edge-on, in two Fornax dwarf galaxies, FCC204 (dS0(6)) and FCC288 (dS0(7)). This is the first time such structures have been identified in Fornax dwarfs. FCC2088 has only a small bulge and a bright flaring and slightly warped disk that can be traced out to 23" from the center (2.05 kpc for H_0=75 km/s/Mpc). FCC204's disk can be traced out to 20" (1.78 kpc). This galaxy possesses a large bulge. These results can be compared to the findings of Jerjen et al. (2000) and Barazza et al. (2002) who discovered nucleated dEs with spiral and bar features in the Virgo Cluster.

Ages and Metallicities of Fornax Dwarf Elliptical Galaxies

Narrowband photometry is presented on 27 dwarf ellipticals in the Fornax cluster. Calibrated with Galactic globular cluster data and spectrophotometric population models, the colors indicated that dwarf ellipticals have a mean [Fe/H] of -1.00 ± 0.28 ranging from -1.6 to -0.4. The mean age of dwarf ellipticals, also determined photometrically, is estimated at 10 ± 1 Gyr compared with 13 Gyr for bright Fornax ellipticals. Comparison of our metallicity color and Mg2 indices demonstrates that the [Mg/Fe] ratio is lower in dwarf ellipticals than their more massive cousins, which is consistent with a longer duration of initial star formation to explain their younger ages. There is a increase in dwarf metallicity with distance from the Fornax cluster center, where core galaxies are on average 0.5 dex more metal-poor than halo dwarfs. In addition, we find the halo dwarfs are younger in mean age compared with core dwarfs. One possible explanation is that the intracluster medium ram pressure strips the gas from dwarf ellipticals, halting star formation (old age) and stopping enrichment (low metallicity) as they enter the core.

Structure of the globular clusters in the Fornax dwarf elliptical galaxy

view Abstract Citations (17) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Structure of The Globular Cluster in The Fornax Dwarf Elliptical Galaxy Rodgers, A. W. ; Roberts, W. H. Abstract We have measured the radial light profiles of the five brighter clusters in the Fornax dwarf elliptical galaxy. We find that the clusters fall into two structural groups. Hodge clusters Nos. 1 and 2 have similar core radii which are twice the core radii of clusters Nos. 3, 4, and 5. Clusters Nos. 1 and 2 appear to fit truncated King models. Clusters Nos. 3, 4, and 5 do not fit the King models but show an extended halo structure with no evidence of tidal truncation. We conjecture that clusters Nos. 1 and 2 have interacted dynamically with each other while the other clusters have had no such interaction over their lifetime. Publication: The Astronomical Journal Pub Date: May 1994 DOI: 10.1086/116982 Bibcode: 1994AJ....107.1737R Keywords: Astronomical Photometry; Dwarf Galaxies; Elliptical Galaxies; Galactic Structure; Globular Clusters; Radial Distribution; Stellar Luminosity; Charge Coupled Devices; Data Reduction; Optical Filters; Telescopes; Astronomy; GALAXIES: PECULIAR; GLOBULAR CLUSTERS: GENERAL; GALAXIES: INDIVIDUAL: FORNAX full text sources ADS | data products SIMBAD (6) NED (6)

Extragalactic globular clusters. III - Metallicity comparisons and anomalies

view Abstract Citations (262) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Extragalactic Globular Clusters. III. Metallicity Comparisons and Anomalies Brodie, Jean P. ; Huchra, John P. Abstract Using a method based on the strengths of six absorption line indices measured in integrated spectra, we have derived metallicities for 22 globular clusters associated with the Sc galaxy, M33, 10 globular clusters associated with the giant elliptical galaxy, M87, eight globular clusters associated with the Sb(r)I-II galaxy, M81, and three globular clusters associated with the Fornax dwarf elliptical galaxy. In addition, we have derived mean metallicities for 38 bright galaxies, mostly ellipticals, 29 dwarf elliptical galaxies in the Virgo cluster, 10 dwarf elliptical galaxies in the Fornax cluster and four local group dwarf galaxies. Comparing these results with metallicities we previously derived for 149 clusters in M31 and with the Milky Way cluster metallicities, we show that the mean metallicity of a cluster system is linearly related to the luminosity of the parent galaxy. A similar relationship is suggested between galaxy metallicity and luminosity for the bright and dwarf galaxies, although metallicity is not the only parameter differentiating the spectroscopic properties of galaxies. The slope of the relationshIp between the mean metallicity of a cluster system and parent galaxy luminosity is very similar to the slope of the relationship between galaxy metallicity and luminosity, but there is an offset in the sense that the clusters are more metal poor. Investigation of the distribution of 12 different line strength indices versus metallicity for clusters and galaxies shows a remarkable uniformity in abundance characteristics among these diverse populations. The only apparent abundance anomalies are in the strengths of cyanogen (4170 A) and the Ca II H and K lines, both of which are enhanced in M31 globular clusters Publication: The Astrophysical Journal Pub Date: September 1991 DOI: 10.1086/170492 Bibcode: 1991ApJ...379..157B Keywords: Abundance; Dwarf Galaxies; Elliptical Galaxies; Globular Clusters; Metallicity; Absorption Spectra; Astronomical Spectroscopy; Calcium; Cyanogen; H Lines; K Lines; Astrophysics; CLUSTERS: GLOBULAR; GALAXIES: STELLAR CONTENT; STARS: ABUNDANCES full text sources ADS | data products SIMBAD (117) NED (78) Related Materials (3) Part 1: 1990ApJ...362..503B Part 2: 1991ApJ...370..495H Part 4: 1996ApJS..102...29H

SPECTROSCOPY OF THE GLOBULAR CLUSTERS IN THE FORNAX DWARF ELLIPTICAL GALAXY

ABSTRACT Spectral observations of the integrated light of four of the globular clusters in the Fornax dwarf elliptical galaxy are discussed. A velocity dispersion of 4.7 km s-1^ is found from data which have a mean differential velocity error of 1.7 km s-1^. This dispersion leads to an estimate of M/Lv_ = 2.3 for the galaxy. The systemic heliocentric velocity is found to be +45 ± 13 km s-1^. The spectral show absorption line strengths which are consistent with estimates by Buonanno et al. (1985) of the cluster metallicities and reinforce the conclusions of Fusi-Pecci (1987) concerning the variation of HB morphologies among the metal-weak, nonnuclear, clusters in the galaxy.

The structure of the Fornax dwarf elliptical galaxy. II - Two-dimensional structure

The structure of the Fornax dwarf elliptical galaxy. II - Two-dimensional structure

The structure of the Fornax dwarf elliptical galaxy. I - The radial profile

view Abstract Citations (37) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Structure of the Fornax Dwarf Elliptical Galaxy. I. The Radial Profile Eskridge, Paul B. Abstract The radial profile of the Fornax dwarf elliptical galaxy has been determined from automated starcounts on UK Schmidt Telescope Unit (UKSTU) plates. The ellipticity (e=0.30 +/- 0.02) and position angle (P.A.(1950.0)=40.2^deg^ +/- 2.0^deg^) are in agreement with the results from the deepest data of Hodge and Smith (1974). The profiles obtained for the four plates have been compared with King (1966) models with a wide range of core and tidal radii. The best overall fit, with some variation from plate to plate, is a model with r_t_ =108' +/- 3' and r_c_ = 16.7' +/- 1.8', with a standard deviation of σ= 1.20 and a reduced χ^2^ of 1.02. This value of the core radius is in essential agreement with previous studies. The tidal radius determined is somewhat larger than found by de Vaucouleurs and Ables (1968) or by Hodge and Smith (1974). Using the above values, along with data from the literature, and including the results from a similar calculation based on data for the Sculptor profile (Eskridge 1988b), the formal result for the mass of the Galaxy is found to be M_G_ ~3.7 +/- 1.9 X 10^10^ M_sun_. This is an unacceptably low value given the current accepted values for R_0_ (8.5 kpc) and v_0_ (220 km/s), and is far lower than recent determinations (Olszewski et al. 1986; Little and Tremaine 1986). This argues that the halo dwarfs have not yet reached tidal equilibrium. Exponential law fits have also been made, following the suggestion (Faber and Lin 1983) that the halo dwarfs are as well fit by exponential laws as are many disk systems. The mean best fit has a slope of γ= -0.040 +/- 0.002 arcmin^-1^, with a standard deviation of σ = 2.32 and a reduced χ^2^ of 0.96. Given the distance modulus of Buonanno et al. (1985), this implies a physical scale length of r_e_ ~0.95 kpc. The larger value of σ for the exponential fit argues that a King model is the better description of the Fornax system. However, while the data show deviations from an exponential law in both the innermost and outermost regions, these are not more severe than deviations seen in a number of disk systems. The current data, therefore, do not argue strongly against the hypothesis that the halo dwarfs are the results of ram-pressure stripping of dI systems by the Galactic halo. Publication: The Astronomical Journal Pub Date: October 1988 DOI: 10.1086/114884 Bibcode: 1988AJ.....96.1352E Keywords: Dwarf Galaxies; Elliptical Galaxies; Galactic Structure; Schmidt Telescopes; Star Formation; Stellar Luminosity; Galactic Rotation; Stellar Models; Astrophysics; GALAXIES: INDIVIDUAL; GALAXIES: LOCAL GROUP; GALAXIES: THE GALAXY; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (2) NED (1) Related Materials (1) Part 2: 1988AJ.....96.1614E

The global luminosity function of the Fornax dwarf elliptical galaxy

view Abstract Citations (12) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Global Luminosity Function of the Sculptor Dwarf Elliptical Galaxy Eskridge, Paul B. Abstract The global luminosity function for the Fornax dwarf elliptical galaxy has been determined from UK Schmidt plates in B and V. The functions do not extend below the horizontal-branch (HB) peak, and thus provide information on only the bright giants. Both functions show evidence of structure in the giant branch. Comparisons are made with luminosity functions (LFs) of globular clusters covering a range in metallicity similar to that found in the Fornax system. These comparisons indicate the old population of Fornax is similar to that of such moderately metal-poor clusters as M5 and M13. They also demonstrate vividly the existence of a significant excess population of very bright stars over that seen in pure old systems. Comparisons are also made with theoretical luminosity functions of various ages and helium abundances. Publication: The Astronomical Journal Pub Date: December 1987 DOI: 10.1086/114588 Bibcode: 1987AJ.....94.1564E Keywords: Dwarf Galaxies; Elliptical Galaxies; Functions (Mathematics); Giant Stars; Spectrum Analysis; Stellar Luminosity; Abundance; Helium; Stellar Evolution; Stellar Mass; Stellar Models; Astrophysics; GALAXIES: GENERAL full text sources ADS | data products SIMBAD (6) NED (2)

The Planetary Nebula in the Fornax Dwarf Galaxy

A planetary nebula has been identified near the center of the Fornax dwarf elliptical galaxy. Quantitative spectrophotometry reveals that it is slightly reddened, and belongs to an intermediate-excitation class, with a normal helium abundance. Since the abundances of all 2 to 3 times lower than in the Orion nebula, the material in the nebula which has a mass ≥ 0.1 M probably represents at least a second generation of processed matter. The implications of this conclusion are briefly discussed from the point of view of heavy element enrichment in low mass systems such as Fornax whose mass is 2×107 M. (Paper will appear in The Astrophysical Journal.)