Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
The Molecular Interstellar Medium of Dwarf Galaxies on Kiloparsec Scales: A New Survey for CO in Northern, IRAS-detected Dwarf Galaxies
We present a new survey for CO in dwarf galaxies using the ARO Kitt Peak12 m telescope. This survey consists of observations of the centralregions of 121 northern dwarfs with IRAS detections and no known COemission. We detect CO in 28 of these galaxies and marginally detectanother 16, increasing by about 50% the number of such galaxies known tohave significant CO emission. The galaxies we detect are comparable instellar and dynamical mass to the Large Magellanic Cloud, althoughsomewhat brighter in CO and fainter in the far-IR. Within dwarfs, wefind that the CO luminosity LCO is most strongly correlatedwith the K-band and the far-infrared luminosities. There are also strongcorrelations with the radio continuum (RC) and B-band luminosities andlinear diameter. Conversely, we find that far-IR dust temperature is apoor predictor of CO emission within the dwarfs alone, although a goodpredictor of normalized CO content among a larger sample of galaxies. Wesuggest that LCO and LK correlate well because thestellar component of a galaxy dominates the midplane gravitational fieldand thus sets the pressure and density of the atomic gas, which controlthe formation of H2 from H I. We compare our sample with moremassive galaxies and find that dwarfs and large galaxies obey the samerelationship between CO and the 1.4 GHz RC surface brightness. Thisrelationship is well described by a Schmidt law withΣRC~Σ1.3CO. Therefore,dwarf galaxies and large spirals exhibit the same relationship betweenmolecular gas and star formation rate (SFR). We find that this result isrobust to moderate changes in the RC-to-SFR and CO-to-H2conversion factors. Our data appear to be inconsistent with large (orderof magnitude) variations in the CO-to-H2 conversion factor inthe star-forming molecular gas.
| Galaxy flow in the Canes Venatici I cloud
We present an analysis of Hubble Space Telescope/WFPC2 images ofeighteen galaxies in the Canes Venatici I cloud. We derive theirdistances from the luminosity of the tip of the red giant branch starswith a typical accuracy of ~ 12%. The resulting distances are 3.9 Mpc(UGC 6541), 4.9 Mpc (NGC 3738), 3.0 Mpc (NGC 3741), 4.5 Mpc (KK 109),>6.3 Mpc (NGC 4150), 4.2 Mpc (UGC 7298), 4.5 Mpc (NGC 4244), 4.6 Mpc(NGC 4395), 4.9 Mpc (UGC 7559), 4.2 Mpc (NGC 4449), 4.4 Mpc (UGC 7605),4.6 Mpc (IC 3687), 4.7 Mpc (KK 166), 4.7 Mpc (NGC 4736), 4.2 Mpc (UGC8308), 4.3 Mpc (UGC 8320), 4.6 Mpc (NGC 5204), and 3.2 Mpc (UGC 8833).The CVn I cloud has a mean radial velocity of 286 +/- 9 kms-1, a mean distance of 4.1 +/- 0.2 Mpc, a radial velocitydispersion of 50 km s-1, a mean projected radius of 760 kpc,and a total blue luminosity of 2.2 x 1010 Lsun .Assuming virial or closed orbital motions for the galaxies, we estimatedtheir virial and their orbital mass-to-luminosity ratio to be 176 and 88Msun /Lsun , respectively. However, the CVn Icloud is characterized by a crossing time of 15 Gyr, and is thus farfrom a state of dynamical equilibrium. The large crossing time for thecloud, its low content of dSph galaxies (<6%), and the almost``primordial'' shape of its luminosity function show that the CVn Icomplex is in a transient dynamical state, driven rather by the freeHubble expansion than by galaxy interactions.Based on observations made with the NASA/ESA Hubble Space Telescope. TheSpace Telescope Science Institute is operated by the Association ofUniversities for Research in Astronomy, Inc. under NASA contract NAS5-26555.Figures 1 and 2 are only available in electronic form athttp://www.edpsciences.org
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Kinematics of AWM and MKW Poor Clusters
We have measured 1365 redshifts to a limiting magnitude of R~15.5 in 15AWM/MKW clusters and have collected another 203 from the literature inMKW 4s, MKW 2, and MKW 2s. In AWM 7 we have extended the redshift sampleto R~18 in the cluster center. We have identified 704 cluster members in17 clusters; 201 are newly identified. We summarize the kinematics anddistributions of the cluster galaxies and provide an initial discussionof substructure, mass and luminosity segregation, spectral segregation,velocity-dispersion profiles, and the relation of the central galaxy toglobal cluster properties. We compute optical mass estimates, which wecompare with X-ray mass determinations from the literature. The clustersare in a variety of dynamical states, reflected in the three classes ofbehavior of the velocity-dispersion profile in the core: rising,falling, or flat/ambiguous. The velocity dispersion of the emission-linegalaxy population significantly exceeds that of the absorption-linegalaxies in almost all of the clusters, and the presence ofemission-line galaxies at small projected radii suggests continuinginfall of galaxies onto the clusters. The presence of a cD galaxy doesnot constrain the global cluster properties; these clusters are similarto other poor clusters that contain no cD. We use the similarity of thevelocity-dispersion profiles at small radii and the cD-like galaxies'internal velocity dispersions to argue that cD formation is a localphenomenon. Our sample establishes an empirical observational baselineof poor clusters for comparison with simulations of similar systems.Observations reported in this paper were obtained at the Multiple MirrorTelescope Observatory, a facility operated jointly by the University ofArizona and the Smithsonian Institution; at the Whipple Observatory, afacility operated jointly by the Smithsonian Astrophysical Observatoryand Harvard University; and at the WIYN Observatory, a joint facility ofthe University of Wisconsin-Madison, Indiana University, YaleUniversity, and the National Optical Astronomy Observatories.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| A CCD survey of galaxies. II. Observations with the 2.1 M telescope at San Pedro Martir
As a part of a CCD survey of galaxies belonging or projected onto theComa and Hercules Superclusters and to the A262, Virgo and Cancerclusters, we present isophote maps and photometric profiles of 87galaxies (85 taken with the V, 25 with the B and 3 with the U Johnsonfilters). For the objects in common we compare our results with those inthe RC3.
| H I deficiency in the Coma I cloud of galaxies
We present new H I observations of galaxies in the Coma I group. Of the32 most probable members of the group, 16 are gas poor and 16 havenormal H I contents. The 16 gas poor galaxies include 4 ellipticals, 5S0s, and 7 spirals with a definite H I deficiency (more than a factor offour). Most of the 16 gas poor or H I deficient galaxies areconcentrated within a radius of 500 kpc of a centroid near the galaxyNGC 4274, suggesting that this region contains a compact core ofintergalactic matter that has stripped the gas from some of thegalaxies. Seven gas poor galaxies are even within a projected radius of130 kpc of this position. This possible existence of a dense core ofintragroup gas may explain the large H I deficiency in the barred spiralNGC 4314. which has 100 times less H I mass than would be expected fromits luminosity and stellar mass. In this galaxy the gas is 99%molecular, 1% atomic and nearly all in the central region. We suspectthe extreme H I deficiency in NGC 4314 is due to two distinct causes:ram pressure stripping of the gas in its outer parts, plus action of itsbar or an ancient tidal interaction with another galaxy that transferredgas from the inner parts of NGC 4314 to the center where H I wasconverted to H_2_.
| A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
| Far-infrared luminosity functions of normal galaxies
A volume-limited sample is constructed from the Zwicky catalog and IRASdata base to examine the FIR luminosity functions of normal galaxies,and to investigate possible relationships between FIR emission andgalaxy morphology. Quantitative and unbiased treatment is provided by'survival analysis' statistical methods. It is found that the FIRdistributions of normal galaxies are better fit by lognormal thanSchechter functions. The total FIR emissivity (8 to 115 microns) ofnormal galaxies is approximately equal to half their emission in the Bplus V optical bands. Normal galaxy FIR emission is uncorrelated withthe basic S0-Sm Hubble sequence of spiral galaxy morphology, but appearsto be affected by de Vaucouleurs' (1959) revised morphologicalclassifications based on inner rings and S-shaped arms. Spirals withbars and inner rings are systematically fainter than unbarred spirals.It is suggested that bars and rings reduce the amount or spatiallyconfine the dust in spiral disks, resulting in lower efficiencyconversion of optical and UV photons into the IR.
| The far-infrared properties of the CfA galaxy sample. I - The catalog
IRAS flux densities are presented for all galaxies in the Center forAstrophysics magnitude-limited sample (mB not greater than 14.5)detected in the IRAS Faint Source Survey (FSS), a total of 1544galaxies. The detection rate in the FSS is slightly larger than in thePSC for the long-wavelength 60- and 100-micron bands, but improves by afactor of about 3 or more for the short wavelength 12- and 25-micronbands. This optically selected sample consists of galaxies which are, onaverage, much less IR-active than galaxies in IR-selected samples. Itpossesses accurate and complete redshift, morphological, and magnitudeinformation, along with observations at other wavelengths.
| Groups of galaxies in the Center for Astrophysics redshift survey
By applying the Huchra and Geller (1982) objective group identificationalgorithm to the Center for Astrophysics' redshift survey, a catalog of128 groups with three or more members is extracted, and 92 of these areused as a statistical sample. A comparison of the distribution of groupcenters with the distribution of all galaxies in the survey indicatesqualitatively that groups trace the large-scale structure of the region.The physical properties of groups may be related to the details oflarge-scale structure, and it is concluded that differences among groupcatalogs may be due to the properties of large-scale structures andtheir location relative to the survey limits.
| Forbidden O III emission in two magnitude-limited field-galaxy surveys
The paper presents emission-line strengths for 394 galaxies from thefield-galaxy redshift surveys of Kirshner, Oemler, and Schechter (1978)and Kirshner et al. (1983) as part of a study of the nature of field andvoid galaxies. These data are 95 percent complete in their coverage ofthe forbidden O III 5007, 4959 A emission lines. It is found that 8.8 +or - 1.5 percent of a J magnitude-limited data set have forbidden O III5007 A emission equivalent widths greater than 10 A. There is noevidence that the spatial distribution of emission-line galaxies in eachfield differs from that of galaxies without emission. However, there isa significant increase in the fraction of galaxies with strong forbiddenO III emission in the southern fields of the Kirshner, Oemler, andSchechter (1978) survey as compared with the other survey fields. Theresults are consistent with the conclusion that the fraction of galaxieswith emission is larger in the Bootes void than in the general field,but tighter constraints on the void normal galaxy population are neededto improve the statistics.
| The spatial distribution of dwarf galaxies in the CfA slice of the universe
A complete (with the the exception of one) redshift sample of 58galaxies in the Nilson catalog classified as dwarf, irregular, orMagellanic irregular is used to investigate the large-scale clusteringproperties of these low-surface brightness galaxies in the CfA slice ofthe universe (alpha in the range of 8-17 h, delta in the range of26.5-32.5 deg). It is found that the low-surface brightness dwarfgalaxies also lie on the structures delineated by the high-surfacebrightness normal galaxies and that they do not fill in the voids. Thisis inconsistent with a class of biased galaxy formation theories whichpredict that dwarf galaxies should be present everywhere, including thevoids.
| KISO survey for ultraviolet-excess galaxies. VI.
Not Available
| HI-observations of galaxies in the Kraan-Korteweg - Tammann catalogue of nearby galaxies. I - The data
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986A&AS...63..323H&db_key=AST
| A survey of galaxy redshifts. IV - The data
The complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s.
| A catalog of hierarchical subclustering in the Turner-Gott groups
Information on the substructure, to four levels of hierarchy, ispresented for the 103 groups listed by Turner and Gott (TG) in theircatalog of groups of galaxies. All galaxies brighter than Mpg= 14.0 in the region delta is 0 deg or greater and b(II) is 40 deg orgreater that have been assigned group memberships by TG are included.Also listed is the local environmental information for each of thegalaxies, giving the surface density enhancement beta in the galaxy'sneighborhood, calculated at 15 levels in the range beta = 4.6 to 10,000.
| A study of field galaxies. I - Redshifts and photometry of a complete sample of galaxies
As a first step towards a redetermination of the luminosity function andspace distribution of field galaxies, data are presented on amagnitude-limited sample of galaxies in eight fields in the north andsouth galactic polar caps. Redshifts, accurate to about 100 km/s havebeen obtained for 164 of 184 galaxies brighter than J=15.0 (Bapproximately equal to 15.5). Magnitudes and colors have also beenmeasured for a large sample of 807 galaxies, complete to J approximatelyequal to 15.7.
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
Catàlegs i designacions:
|
