Virgo Cluster Core Research Articles

Narrowband Imaging in [O [CSC]iii[/CSC]] and Hα to Search for Intracluster Planetary Nebulae in the Virgo Cluster

We have identified intracluster planetary nebulae (PNs) in a Virgo Cluster core field by imaging with the Subaru Suprime-Cam through two narrowband filters centered at the redshifted wavelengths of the [O III] λ5007 and the Hα 6563 A lines; broadband images in V and R were acquired to check for emission in the adjacent continuum. Emission-line objects in Virgo are then selected from the two-color diagram [O III]-Hα versus [O III]-(V+R), which is calibrated using PNs in M84 (Jacoby et al.). Using both [O III] and Hα allows us to distinguish bona fide planetary nebulae from high-redshift emission-line galaxies at the bright end of the [O III] luminosity function. Spectroscopic observations of a subsample of these objects were made at the Telescopio Nazionale Galileo and at the Very Large Telescope in a region around M84 and in an intracluster field, respectively. The observations confirm the efficiency of the combined [O III]+Hα imaging to identify true PNs. We also obtained the first spectrum of an intracluster PN that shows the [O III] doublet with a signal-to-noise ratio greater than 10 and its Hα emission. From the results based on the spectroscopic follow-up, we derive a lower limit to the fraction of the Virgo Cluster light contributed by the intracluster stars at the surveyed position in the cluster core: it amounts to 10%.

Intracluster Planetary Nebulae in Virgo: Photometric Selection, Spectroscopic Validation, and Cluster Depth

We have imaged an empty area of 34 × 34 arcmin2 15 north of the Virgo Cluster core to survey for intracluster planetary nebula (PN) candidates. We have implemented and tested a fully automatic procedure for the selection of emission-line objects in wide-field images, based on the on-off technique from Ciardullo and Jacoby. Freeman et al. have spectroscopically confirmed a sample of intracluster planetary nebulae in one Virgo field. We use the photometric and morphological properties of this sample to test our selection procedure. In our newly surveyed Virgo field, 75 objects were identified as best candidates for intracluster PNe. The luminosity function of the spectroscopically confirmed PNe shows a brighter cutoff than the planetary nebula luminosity function for the inner regions of M87. Such a brighter cutoff is also observed in the newly surveyed field and indicates a smaller distance modulus, implying that the front end of the Virgo Cluster is closer to us by a significant amount: 14% closer (2.1 Mpc) than M87 for the spectroscopic field, using the PN luminosity function distance of 14.9 Mpc to M87, and 18% closer (2.8 Mpc) than M87 for the newly surveyed field. Independent distance indicators (Tully-Fisher relation for Virgo spirals and surface brightness fluctuations for Virgo ellipticals) agree with these findings. From these two Virgo Cluster fields there is no evidence that the surface luminosity density for the diffuse stellar component in the cluster decreases with radius. The luminosity surface density of the diffuse stellar population is comparable to that of the galaxies.

Dark Mass–to–Luminous Mass Coupling in Virgo

The empirical relation of coupling in Md = γM1/2r between the halo dark mass distribution Md and visible mass M at radius r, previously shown in spiral galaxies and in the core of MS 2137-2353, is tested for the inner 150 h-1 kpc Virgo Cluster core. If the stellar mass-to-light ratio in M87 is treated as a free parameter, the density distribution predicted by this relation is found to be consistent with that derived from published surface photometry, stellar and globular cluster dynamics, and X-ray observations. The best fit is obtained for ϒ*(M87) = 6 (M/LB)☉, but a wide range of stellar mass-to-light ratios are possible. At r > 50 kpc, the relation of coupling and the equation of dynamical equilibrium of the gas are the same. The extrapolated dark mass is also consistent with the kinematics of early-type galaxies on a larger, megaparsec scale for ϒ*(M87) = 8-11 (M/LB)☉. The cluster dark mass halo and the stellar mass in M87 have equal weight at ~1/2-3/4 effective radius.

TheHubble Space TelescopeKey Project on the Extragalactic Distance Scale. XX. The Discovery of Cepheids in the Virgo Cluster Galaxy NGC 4548

We report on the discovery and properties of Cepheid variable stars in the barred spiral galaxy NGC 4548, which is a member of the Virgo cluster of galaxies. This is one of the galaxies being observed as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale, which aims to determine the Hubble constant to 10% accuracy. Our analysis is based on observations made with the Wide Field and Planetary Camera 2 during 1996 and 1997. We identify 24 probable Cepheids with periods between 16 and 38 days. They were observed over 13 epochs with the F555W filter and eight epochs with the F814W filter. The HST F555W and F814W data have been transformed to the Johnson V and Cousins I magnitude systems, respectively. Photometry has principally been carried out using the DAOPHOT/ALLFRAME package. A comparison is made with parallel measurements using the DoPHOT package. Apparent period-luminosity relations for V and I have been constructed. Assuming values of μ=18.50±0.10 mag and E(B-V)=0.10 mag for the distance modulus and reddening of the Large Magellanic Cloud, a true distance modulus of 31.01±0.28 mag is derived corresponding to a distance of 15.9±2.0 Mpc. HST Cepheid distances of other spiral galaxies in the Virgo Cluster are discussed. Their good agreement with the new NGC 4548 distance strengthens the evidence that this galaxy lies within the Virgo cluster core.

Intracluster Planetary Nebulae in the Virgo Cluster. I. Initial Results

We report the initial results of a survey for intracluster planetary nebulae in the Virgo Cluster. In two 16' × 16' fields, we identify 69 and 16 intracluster planetary nebula candidates, respectively. In a third 16' × 16' field near the central elliptical galaxy M87, we detect 75 planetary nebula candidates, of which a substantial fraction are intracluster in nature. By examining the number of the planetaries detected in each field and the shape of the planetary nebula luminosity function, we show that (1) the intracluster starlight of Virgo is distributed nonuniformly and varies between subclumps A and B, (2) the Virgo Cluster core extends ~3 Mpc in front of M87, and thus is elongated along the line of sight, and (3) a minimum of 22% of Virgo's stellar luminosity resides between the galaxies in our fields, and the true number may be considerably larger. We also use our planetary nebula data to argue that the intracluster stars in Virgo are likely derived from a population that is of moderate age and metallicity.

The "Virgo photometry catalogue”; a catalogue of 1180 galaxies in the direction of the Virgo Cluster's core

We present a new catalogue of galaxies in the direction of the Virgo Cluster's core: the Virgo Photometry Catalogue (VPC) 1 . This catalogue contains 1180 galaxies (including background objects) within a 23 square-degree area of the sky centred on R:A:1950:0 = 12 h 26 m and dec:1950:0 =1 308 0 . The VPC galaxy sample comprises of non-stellar objects brighter thanBJ25 =1 9 :0; the completeness limits beingBJ25 18:5 for the northern half of the survey area and BJ25 18:0 for the southern half. Independently-calibrated photographic surface pho- tometry is presented for over 1000 galaxies in the U, BJ and RC bands. Parameters listed for catalogued galax- ies include: equatorial coordinates, morphological types, surface-brightness prole parameters (which preserve the majority of the original surface photometry information), U, BJ & RC isophotal magnitudes, BJ and (transformed) B total magnitudes, (U BJ )a nd ( B J R C) equal-area and total colours, apparent angular radii, ellipticities, po- sition angles, heliocentric radial velocities and alternative designations. All total magnitudes and total colours are extrapolated according to a new system denoted t in or- der to distinguish it from the T system already in use. The VPC is based primarily on four (one U ,t wo B J and one RC) UK-Schmidt plates, all of which were digi- tised using the Royal Observatory Edinburgh's (ROE) COSMOS measuring machine. All magnitudes, colours and surface-brightness parameters are derived from nu- merical integrations of segmented plate-scan data, except for (in 109 cases) saturated or (in 51 cases) inextricably-

More Evidence for a Population of Intracluster Planetary Nebulae in the Virgo Cluster

We surveyed a 50 arcmin2 region in the Virgo cluster core to search for intergalactic planetary nebulae and found 11 candidates in the surveyed area. The measured fluxes of these unresolved sources are consistent with these objects being planetary nebulae from an intergalactic population of stars, although we cannot exclude some minor contamination of our sample by redshifted starburst galaxies. We compute the cumulative luminosity function of these 11 planetary nebula candidates. If we assume that they belong to the Virgo cluster, their cumulative luminosity function is in good agreement with planetary nebula luminosity-function simulations for a typical stellar population of ellipticals or spiral bulges. This comparison allows us to estimate the surface mass density of the intergalactic stellar population at the surveyed field in the cluster core.

Globular Cluster Luminosity Functions and the Hubble Constant From WFPC2 Imaging: The Giant Elliptical NGC 4365

view Abstract Citations (25) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Globular Cluster Luminosity Functions and the Hubble Constant From WFPC2 Imaging: The Giant Elliptical NGC 4365 Forbes, Duncan A. Abstract The turnover, or peak, magnitude in a galaxy's globular cluster luminosity function (GCLF) may provide a standard candle for an independent distance estimator. Here we examine the GCLF of the giant elliptical NGC 4365 using photometry of ~350 globular clusters from the Hubble Space Telescope's Wide Field and Planetary Camera 2 (WFPC2). The WFPC2 data have several advantages over equivalent ground-based imaging. The membership of NGC 4365 in the Virgo cluster has been the subject of recent debate. We have fit a Gaussian and t_5_ profile to the luminosity function and find that it can be well represented by a turnover magnitude of m^0^_v_ = 24.2+/-03 and a dispersion σ = 1.28+/-0.15. After applying a small metallicity correction to the "universal" globular cluster turnover magnitude, we derive a distance modulus of (m - M) = 31.6+/-0.3 which is in reasonable agreement with that from surface brightness fluctuation measurements. This result places NGC 4365 about 5 Mpc beyond the Virgo cluster core. For a V_CMB_ = 1592+/-24 km s^-1^ the Hubble constant is H_0_ = 72^+10^_-12_ km s^-1^ Mpc^-1^. We also describe our method for estimating a local specific frequency for the GC system within the central 5 h^-1^ kpc which has fewer uncertain corrections than a total estimate. The resulting value of 6.4+/-1.5 indicates that NGC 4365 has a GC richness similar to other early-type galaxies. Publication: The Astronomical Journal Pub Date: September 1996 DOI: 10.1086/118069 arXiv: arXiv:astro-ph/9611140 Bibcode: 1996AJ....112..954F Keywords: GALAXIES: INDIVIDUAL: NGC 4365; GLOBULAR CLUSTERS: GENERAL; DISTANCE SCALE; Astrophysics E-Print: 12 pages, Latex, full paper also available at http://www.ucolick.org/~forbes/home.html full text sources arXiv | ADS | data products SIMBAD (7) NED (4) MAST (1) ESA (1)

Steps toward the Hubble Constant. X. The Distance of the Virgo Cluster Core Using Globular Clusters

view Abstract Citations (53) References (107) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward the Hubble Constant. X. The Distance of the Virgo Cluster Core Using Globular Clusters Sandage, Allan ; Tammann, G. A. Abstract New data for Secker's (1992) unbiased sample of 100 globular clusters in the Milky Way exhibit a nearly Gaussian luminosity function with peak (turnover) luminosities of <MB>0 = -6.90±0.11, σ(M) = 1.07 mag, and <MV>0 = -760 + 0 11 a(M) = 1.07. These are derived from revised Galactic globular cluster distances determined from an RR Lyrae calibration of Mv(RR) = 0.30 ([Fe/H]) + 0.94 based on the Oosterhoff-Arp-Preston period-metallicity effect. The new calibration averages 0.25 mag brighter than is generally in current use. Halo clusters in M31 give <MB>0 = -7.01±0.20, σ(M) = 0.89, and <MV>0 = -7.70±020 σ(M) = 0.89 for the globular cluster luminosity function (GCLF) using a Cepheid modulus for M31 of (m - M)° = 24.44 (Madore & Freedom 1991) with a foreground reddening of E(B- V) = 0.08. Use of the brighter RR Lyrae magnitudes for the MW calibrators nearly eliminates the marginal 0.2-0.3 mag difference between the MW and the M31 GCLFs obtained earlier by Racine & Harris (1992) and Secker (1992). The combined globular cluster luminosity function for the MW plus M31 gives <MB>0(turnover) = -6.93±0.08 and <MV>0(turnover) = -7.62±0.08, with a realistic external error of ∼0.2 mag. Applying this local calibration to the E galaxy Virgo cluster data gives the modulus of the Virgo cluster core as (m-M)° = 31.64±0.25 (D = 21.3±2.7 Mpc; external error). This value is based on the observed mean GCLF turnover luminosity of <B>0 = 24.64±0.07 for three galaxies as determined by Harris et al. (1991). The modulus is only marginally increased if NGC 4365 is accepted as a likely Virgo cluster member and if new data for NGC 4636 are included. We have used the precept that the mean absolute turnover luminosity of the GCLF is universal, that is, does not depend on a second parameter. The suggestion (Secker & Harris 1993) that the turnover luminosity varies with the dispersion of the GCLF, based on their a priori adoption of a short-distance-scale modulus of the Virgo cluster as (m-M)° = 30.89, is discussed. Contrary, independent evidence that the modulus of the Virgo cluster core is (m-M)° = 31.7 is reviewed. The Hubble constant, based on (1) the distance to the Virgo cluster core determined from the calibration of the globular cluster method given here, and (2) the redshift of the Virgo core of υ(cosmic) = 1179±17 km s-1 relative to the Machian frame of the cosmic microwave background, freed from all local streaming motions (Jerjen & Tammann 1993), is H0(global) = 55±7 km s-1 Mpc-1 (external error). Publication: The Astrophysical Journal Pub Date: June 1995 DOI: 10.1086/175761 Bibcode: 1995ApJ...446....1S Keywords: COSMOLOGY: DISTANCE SCALE; GALAXIES: CLUSTERS: INDIVIDUAL NAME: VIRGO; GALAXIES: DISTANCES AND REDSHIFTS; GALAXIES: STAR CLUSTERS full text sources ADS | data products SIMBAD (98) NED (7) Related Materials (9) Part 1: 1974ApJ...190..525S Part 2: 1974ApJ...191..603S Part 3: 1974ApJ...194..223S Part 4: 1974ApJ...194..559S Part 5: 1975ApJ...196..313S Part 6: 1975ApJ...197..265S Part 7: 1976ApJ...210....7S Part 8: 1982ApJ...256..339S Part 9: 1990ApJ...365....1S

Steps toward the Hubble constant. IX - The cosmic value of H(0) freed from all local velocity anomalies

view Abstract Citations (123) References (133) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steps toward the Hubble Constant. IX. The Cosmic Value of H 0 Freed from All Local Velocity Anomalies Sandage, Allan ; Tammann, G. A. Abstract The velocity which the Virgo Cluster would have if it were freed from all local anomalies relative to the cosmological Machian frame is determined by bringing the remote velocity frame to the Virgo Cluster distance. Three independent methods are used to accomplish this: (1) distances of 17 "remote" clusters are determined relative to Virgo by a number of independent methods; the equation of the Hubble diagram correlation that relates redshift and the distance modulus difference from Virgo is then read for its velocity value at the modulus difference of {DELTA}(m-M) = 0.00; (2) a similar calculation is made using apparent magnitudes of first-ranked cluster galaxies in relatively distant clusters, and (3) the same calculation is made using distant supernovae of Type Ia. The resulting velocity of Virgo, called the "cosmic expansion velocity freed from local velocity anomalies" is v_cosmic_(Virgo) = 1144 +/- 18 km s^-1^. The distance to the Virgo Cluster core is determined from six independent methods using recent data, giving (m-M) = 31.70 +/- 0.09, or D = 21.9 +/- 0.9 Mpc. Combining the cosmic Virgo velocity with this distance, which now is of unprecedented accuracy, gives the Hubble constant to be H_0_ = 52 +/- 2 km s^-1^ Mpc^-1^. If a still more accurate distance D (in Mpc) to the Virgo Cluster core becomes available, the calculated Hubble constant will be changed to H_0_ = 52(21.9/D) km s^-1^ Mpc^-1^. As a by-product (but which does not enter the method devised here to find H_0_), we determine the infall velocity of the Local Group toward Virgo (the retarded expansion effect) to be 168 +/- 50 km s^-1^. A firm lower limit to H_0_ can be obtained by putting this infall velocity to zero so that v(Virgo)_cosmic_ = v(Virgo)_observed_ = 976 +/- 45 km s^-1^. For this limiting case (which is physically unreal unless the Virgo pull is zero, and therefore {DELTA} = 0) the lower limit to the global value of H_0_ becomes H_0(min)_ = (45 +/- 3)(21.9/D) km s^-1^ Mpc^-1^. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/169453 Bibcode: 1990ApJ...365....1S Keywords: Cosmology; Hubble Constant; Virgo Galactic Cluster; Andromeda Galaxy; Interstellar Matter; Local Group (Astronomy); Planetary Nebulae; Red Shift; Spatial Distribution; Astrophysics; COSMOLOGY; GALAXIES: CLUSTERING; GALAXIES: DISTANCES; GALAXIES: REDSHIFTS full text sources ADS | data products SIMBAD (19) NED (17) Related Materials (9) Part 1: 1974ApJ...190..525S Part 2: 1974ApJ...191..603S Part 3: 1974ApJ...194..223S Part 4: 1974ApJ...194..559S Part 5: 1975ApJ...196..313S Part 6: 1975ApJ...197..265S Part 7: 1976ApJ...210....7S Part 8: 1982ApJ...256..339S Part 10: 1995ApJ...446....1S

The Hubble constant from Pritchet and von den Bergh's nova distance to the Virgo cluster

Two reasons are offered why the value for H(0) of 69 + or - 14 km/s/Mpc of Pritchet and van den Bergh (1987) is likely to be too high by about 20 percent even when their value of 6.8 + or - 0.4 for the M31-Virgo modulus difference is adopted. One reason concerns the free expansion velocity of the Virgo cluster core and the other concerns the apparent distance modulus of M31. Reasons for adopting a global H(0) value of 56 + or - 12 km/s/Mpc are discussed. 25 references.

The pattern of H I deficiency in the Virgo cluster

view Abstract Citations (125) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Pattern of H i Deficiency in the Virgo Cluster Haynes, M. P. ; Giovanelli, R. Abstract A sample of 160 galaxies in the Virgo region, including 16 new 21-cm profiles in the Virgo 5-degree core obtained with the 305-m Arecibo telescope, are examined to investigate the severe depletion of interstellar H I within spiral galaxies in the Virgo cluster core. A similar and non-Gaussian distribution is found for the distribution of H I deficiencies of both faint galaxies and brighter spirals, and populations of galaxies with normal abundances of interstellar H I, and those of gas poor objects exhibiting a late-type morphology, are both noted. One-sixth of the sample within the Virgo 5-degree core have lost more than 90 percent by mass of their original neutral hydrogen, and three quarters of the galaxies found within 2.5 degrees of M87 are H I poor by more than a factor of three. The most deficient galaxies are also found to be the ones with the smallest ratios of H I to optical disk size, and H I poor galaxies are redder than normal, indicating that star formation has been quenched. Publication: The Astrophysical Journal Pub Date: July 1986 DOI: 10.1086/164357 Bibcode: 1986ApJ...306..466H Keywords: Hydrogen; Interstellar Gas; Radio Astronomy; Virgo Galactic Cluster; Centimeter Waves; Line Spectra; Red Shift; Astrophysics; GALAXIES: CLUSTERING; INTERSTELLAR: MATTER; RADIO SOURCES: 21 CM RADIATION full text sources ADS | data products SIMBAD (68) NED (67)

Candidate Galaxies for Study of the Local Velocity Field and Distance Scale Using Space Telescope - Part Three - Galaxies in the Virgo Cluster Core

Candidate Galaxies for Study of the Local Velocity Field and Distance Scale Using Space Telescope - Part Three - Galaxies in the Virgo Cluster Core

Candidate galaxies for study of the local velocity field and distance scale using Space Telescope. I - The most easily resolved. II - The more difficult cases. III - Galaxies in the Virgo cluster core

Photographs for 95 nearby galaxies that have promise of high resolution into individual stars with Space Telescope are illustrated in 21 panels of an atlas. The criteria used to choose the candidates are (1) low surface brightness of either the whole of the galaxian disk or those parts of the disk threaded by spiral arms, (2) spiral arms that are sparse enough to resolve into stars with an effective crowding no worse than in M33 and M101 from the ground, but scaled to a resolution of ≡0.1 arcsec, and (3) distances no greater than ≡70 Mpc - a value that follows from criterion (2). Some of the 95 candidate galaxies can be resolved into brightest red and blue stars and Cepheids at superior seeing sites from the ground, and such a subset of the sample is indicated. A strategy for a perspicacious selection of the candidate galaxies is outlined for an experiment to test and to map accurately the Virgocentric velocity perturbation model. The strategy is illustrated using the Tonry-Davis and the Kraan-Korteweg perturbation diagrams.

A sensitive H I detection survey for early-type disk galaxies

view Abstract Citations (57) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A sensitive HI detection survey for early-type disk galaxies. Giovanardi, C. ; Krumm, N. ; Salpeter, E. E. Abstract A sensitive neutral hydrogen study was carried out on a sample of 145 galaxies with known redshift and with Hubble classification S0, S0/a, or Sa. New H I data were collected with the 305 m Arecibo telescope. The study covers galaxies both in and outside of the Virgo cluster, includes some faint galaxies (to mz = 14.0), and used only one central Arecibo beam per galaxy. In total, 64 galaxies are detected, including 25 pure S0 galaxies. However, in spite of the good sensitivity, many of the S0 galaxies are still undetected (while others give a very strong signal), indicating a very large range in the ratio of hydrogen mass to luminosity. The authors confirm that the detection probability for S0 galaxies is smaller inside the Virgo cluster than outside. Most Sa galaxies were detected, except in the Virgo cluster core, and the H I content of detected Sa galaxies is smaller inside the cluster than outside. The correlation of gas content with optical features and radio continuum properties is also discussed. Publication: The Astronomical Journal Pub Date: December 1983 DOI: 10.1086/113464 Bibcode: 1983AJ.....88.1719G Keywords: Centimeter Waves; Disk Galaxies; Galactic Radio Waves; Hydrogen Clouds; Neutral Gases; Virgo Galactic Cluster; Astronomical Coordinates; Continuous Spectra; Galactic Structure; Mass To Light Ratios; Spatial Distribution; Astrophysics full text sources ADS | data products SIMBAD (144) NED (144)

Effects of environment on neutral hydrogen distribution for disk galaxies in the Virgo Cluster area

A statistical analysis is carried out on H I observations of galaxies, which include mapping with the Arecibo beam (reported in previous papers), both inside and outside the direction of the Virgo cluster core (radius 5/sup 0/ or 6/sup 0/). The galaxies were classified both according to the revised Hubble (RH) scheme and the RDDO scheme suggested by van den Bergh. SO galaxies on the RH scheme have a larger detection probability outside than inside; ''true SO'' galaxies on the RDDO scheme have a small detection probability everywhere; ''anemics'' have a larger detection probability and are more common outside the cluster core. Anemic and spiral galaxies of all types have an average H I mass content M/sub H/ which is smaller inside the Virgo cluster core by a factor of about 2 to 2.5 than galaxies of the same type outside the core. This result agrees with that obtained by Chamaraux et al., using different methods, and seems now firmly established. H I diameters D/sub H/, defined in terms of a scale length, are also smaller inside the core than outside so that the surface density sigma/sub H/proportionalM/sub H//D/sub H//sup 2/ is almost the same inside and outside (always comparingmore » galaxies of the same morphological type). Ram pressure stripping of an outer galactic disk by intracluster gas predicts just such results. By contrast, ''anemics'' have almost the same D/sub H/ as a ''true spirals'' (or even larger) but smaller sigma/sub H/, suggesting they lost hydrogen gas by some means other than stripping.« less

Neutral hydrogen distribution and velocity structure of some early-type galaxies

view Abstract Citations (59) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Neutral hydrogen distribution and velocity structure of some early-type galaxies. Krumm, N. ; Salpeter, E. E. Abstract Sixteen disk galaxies of early type, detected in a systematic survey, were mapped in neutral hydrogen with the 3.2-arcmin Arecibo beam. More than half of the galaxies have extended neutral hydrogen emission. Hydrogen masses and radii tend to be smaller for galaxies in the Virgo cluster core than outside of it. Galaxies with extended emission satisfy a 'Tully-Fisher relation' (velocity width versus luminosity) similar to that for late-type spirals. For five galaxies a rotation curve was obtained: three of the curves are flat, and two appear similar to that of M81. Mass-to-luminosity ratios estimated for these five cases are also similar to those for spirals. For at least two galaxies (possibly four) the 21 cm line has a very narrow profile, and the neutral hydrogen must be concentrated in a small region near the nucleus. Publication: The Astrophysical Journal Pub Date: February 1979 DOI: 10.1086/156822 Bibcode: 1979ApJ...228...64K Keywords: Galactic Clusters; Hydrogen Clouds; Mass Distribution; Radio Galaxies; Spiral Galaxies; Velocity Distribution; Galactic Nuclei; Galactic Rotation; Line Spectra; Luminous Intensity; Microwave Emission; Neutral Particles; Astrophysics; Clusters of Galaxies:Virgo; Early-Type Galaxies:Neutral Hydrogen; Galaxies:Internal Motions full text sources ADS | data products NED (18)

Membership and velocity distribution in the core of the Virgo cluster

The question has been raised of whether some bright spirals with negative velocities and large angular diameters are true members of the Virgo cluster core or close foreground objects. Observations of 21-cm spectral profiles for seven of the negative-velocity galaxies are examined. By using the Fisher-Tully (1977) method (correlation between luminosity and velocity width), it is shown that these galaxies are at the distance of the Virgo cluster and tend to have large masses. Spirals in the Virgo cluster core have a mean velocity similar to that of the ellipticals and lenticulars but a larger velocity dispersion (about the cluster mean). The possibility is considered that low-velocity spirals may have been converted into some form of lenticulars by tidal stripping of their outer disks.