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|Red Thick Disks of Nearby Galaxies|
Edge-on systems reveal the properties of disk galaxies as a function ofheight, z, above the plane. Four local edge-on galaxies that are closeenough to have been resolved into stars by the Hubble Space Telescopeshow thick disks composed of a red stellar population that is old andrelatively metal rich. Color gradients, Δ(V-I)/Δz, are zeroor slightly positive. Favored models may have an explicit thick diskformation phase.
|A Catalog of Neighboring Galaxies|
We present an all-sky catalog of 451 nearby galaxies, each having anindividual distance estimate D<~10 Mpc or a radial velocityVLG<550 km s-1. The catalog contains data onbasic optical and H I properties of the galaxies, in particular, theirdiameters, absolute magnitudes, morphological types, circumnuclearregion types, optical and H I surface brightnesses, rotationalvelocities, and indicative mass-to-luminosity and H I mass-to-luminosityratios, as well as a so-called tidal index, which quantifies the galaxyenvironment. We expect the catalog completeness to be roughly 70%-80%within 8 Mpc. About 85% of the Local Volume population are dwarf (dIr,dIm, and dSph) galaxies with MB>-17.0, which contributeabout 4% to the local luminosity density, and roughly 10%-15% to thelocal H I mass density. The H I mass-to-luminosity and the H Imass-to-total (indicative) mass ratios increase systematically fromgiant galaxies toward dwarfs, reaching maximum values about 5 in solarunits for the most tiny objects. For the Local Volume disklike galaxies,their H I masses and angular momentum follow Zasov's linear relation,expected for rotating gaseous disks being near the threshold ofgravitational instability, favorable for active star formation. We foundthat the mean local luminosity density exceeds 1.7-2.0 times the globaldensity, in spite of the presence of the Tully void and the absence ofrich clusters in the Local Volume. The mean local H I density is 1.4times its ``global'' value derived from the H I Parkes Sky Survey.However, the mean local baryon densityΩb(<8Mpc)=2.3% consists of only a half of the globalbaryon density, Ωb=(4.7+/-0.6)% (Spergel et al.,published in 2003). The mean-square pairwise difference of radialvelocities is about 100 km s-1 for spatial separations within1 Mpc, increasing to ~300 km s-1 on a scale of ~3 Mpc. alsoWe calculated the integral area of the sky occupied by the neighboringgalaxies. Assuming the H I size of spiral and irregular galaxies to be2.5 times their standard optical diameter and ignoring any evolutioneffect, we obtain the expected number of the line-of-sight intersectionswith the H I galaxy images to be dn/dz~0.4, which does not contradictthe observed number of absorptions in QSO spectra.
|First results from the HI Jodrell All Sky Survey: inclination-dependent selection effects in a 21-cm blind survey|
Details are presented of the HI Jodrell All Sky Survey (HIJASS). HIJASSis a blind neutral hydrogen (HI) survey of the northern sky (δ> 22°), being conducted using the multibeam receiver on theLovell Telescope (full width at half-maximum beamwidth 12 arcmin) atJodrell Bank. HIJASS covers the velocity range -3500 to 10 000 kms-1, with a velocity resolution of 18.1 km s-1 andspatial positional accuracy of ~2.5 arcmin. Thus far about 1115deg2 of sky have been surveyed. The average rms noise duringthe early part of the survey was around 16 mJy beam-1.Following the first phase of the Lovell Telescope upgrade (in 2001), therms noise is now around 13 mJy beam-1. We describe themethods of detecting galaxies within the HIJASS data and of measuringtheir HI parameters. The properties of the resulting HI-selected sampleof galaxies are described. Of the 222 sources so far confirmed, 170 (77per cent) are clearly associated with a previously catalogued galaxy. Afurther 23 sources (10 per cent) lie close (within 6 arcmin) to apreviously catalogued galaxy for which no previous redshift exists. Afurther 29 sources (13 per cent) do not appear to be associated with anypreviously catalogued galaxy. The distributions of peak flux, integratedflux, HI mass and cz are discussed. We show, using the HIJASS data, thatHI self-absorption is a significant, but often overlooked, effect ingalaxies with large inclination angles to the line of sight. Properlyaccounting for it could increase the derived HI mass density of thelocal Universe by at least 25 per cent. The effect that this will haveon the shape of the HI mass function will depend on how self-absorptionaffects galaxies of different morphological types and HI masses. We alsoshow that galaxies with small inclinations to the line of sight may alsobe excluded from HI-selected samples, since many such galaxies will haveobserved velocity widths that are too narrow for them to bedistinguished from narrow-band radio-frequency interference. This effectwill become progressively more serious for galaxies with smallerintrinsic velocity widths. If, as we might expect, galaxies with smallerintrinsic velocity widths have smaller HI masses, then compensating forthis effect could significantly steepen the faint-end slope of thederived HI mass function.
|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
|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.
|Multi-colour photometry of nearby dwarf galaxies|
Observations of 39 nearby, mostly dwarf galaxies are presented. Theobservations were carried out at the 1.2-m telescope of Observatoire deHaute-Provence (France) with B, V and I Cousins filters. Based onsurface and integrated photometry of the obtained images we derivedtotal B, V and I magnitudes and integrated B-V, V-I colours as well asradii and magnitudes at the 25 m isophotal level. Azimuthally averagedsurface brightness profiles were derived for 33 galaxies in eachphotometric band. Most of the profiles can be well fitted by anexponential intensity law of brightness distribution. The best-fittingexponential parameters are also given for the galaxies. Based onobservations made at Observatoire de Haute Provence (CNRS), France.Table 3 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (126.96.36.199) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|HI properties of nearby galaxies from a volume-limited sample|
We consider global HI and optical properties of about three hundrednearby galaxies with V_0 < 500 km s(-1) . The majority of them haveindividual photometric distance estimates. The galaxy sample parametersshow some known and some new correlations implying a meaningful dynamicexplanation: 1) In the whole range of diameters, 1 - 40 Kpc, the galaxystandard diameter and rotational velocity follows a nearly linearTully-Fisher relation, lg A25~(0.99+/-0.06)lg V_m. 2) The HImass-to-luminosity ratio and the HI mass-to-``total" mass (inside thestandard optical diameter) ratio increase systematically from giantgalaxies towards dwarfs, reaching maximum values 5 ;M_ȯ/L_ȯand 3, respectively. 3) For all the Local Volume galaxies their totalmass-to-luminosity ratio lies within a range of [0.2-16]M_ȯ/L_ȯ with a median of 3.0 ;M_ȯ/L_ȯ. TheM25/L ratio decreases slightly from giant towards dwarfgalaxies. 4) The M_HI/L and M25/L ratios for the samplegalaxies correlate with their mean optical surface brightness, which maybe caused by star formation activity in the galaxies. 5) The M_HI/L andM25/L ratios are practically independent of the local massdensity of surrounding galaxies within the range of densities of aboutsix orders of magnitude. 6) For the LV galaxies their HI mass andangular momentum follow a nearly linear relation: lgM_HI~(0.99+/-0.04)lg (V_m* A25), expected for rotatinggaseous disks being near the threshold of gravitational instability,favourable for active star formation. Table in the Appendix is availableonly in electronic form at the CDS via anonymous ftp 188.8.131.52 orhttp//cdsweb.u-strasbg.fr/Abstract.html
|Detailed images and distance measurements for eighteen dwarf irregular galaxies in the Canes Venatici cloud|
In the Canes Venatici cloud, eighteen dwarf irregular galaxies wereobserved in B, V bands at the Nordic Optical Telescope under a seeing ofone arcsec. Most of the galaxies having radial velocities V_0 < 500km/s have been resolved into stars for the first time. The galaxydistances were derived based on photometry of their brightest bluestars. Distances to some of the galaxies: UGC 6782, UGC 7131 and,probably, K 215, which are located at the CVn southern edge, wereestimated to be about 15 Mpc, which is typical of the Virgo clusteroutskirts. For two LSB galaxies, K 200 and K 215, the distances may beoverestimated, probably because of a lack of young massive stars. Forthe remaining galaxies: UGC 7559, UGC 7599, UGC 7605, UGC 7639, UGC7698, UGCA 290, UGCA 292, UGC 7866, UGC 8024, UGC 8638, UGC 8651, UGC8760, and UGC 8833 the estimated distances range from 2.3 to 8.0 Mpc,indicating their actual membership in the CVn cloud. Several objectsstudied here (UGC 7605, UGC 7639, UGC 8638, UGC 8833) have awell-resolved bluish core and regular yellow outer parts, which maypoint to composite (new and old) populations. The galaxy UGCA 292 = CVndwA has unusual global parameters: (B-V)_T=+0.08, M_T=-11.4, M(HI)/L_B =6\ M_sun/L_sun and M(HI)/M_T =0.7, being, perhaps, one of the youngestknown objects in the Local Universe. Table 2 to 19 are only available atthe CDS via anonymous ftp 184.108.40.206 or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|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.
|KISO survey for ultraviolet-excess galaxies. XVII|
Presented here are the 17th list and identification charts of theUV-excess galaxies which have been detected on the multicolor platestaken with the Kiso Schmidt telescope for 10 survey fields. In the skyarea of some 300 sq deg 379 objects are catalogued down to aphotographic magnitude of about 18.
|21 centimeter study of spiral galaxies in clusters. III - Neutral gas content, star formation, and radio continuum properties|
21 cm line observations of 112 galaxies in seven clusters and inrelatively isolated regions in the Coma 'wall' were secured with theArecibo telescope. These, combined with an available data base, are usedto discuss the relations between the neutral gas column density, thestar formation rate, the FIR, and the radio continuum emission in spiralgalaxies inside and outside rich clusters. It is found thathydrogen-deficient cluster galaxies have star formation rates similar tounperturbed isolated galaxies, confirming that atomic gas ablation inclusters does not alter the supply of molecular gas. The extended radiocontinuum emission of about 30 percent of cluster spirals is higher thanthat of isolated galaxies of similar type at any given gas surfacedensity. A significant fraction of these galaxies is found perturbed intheir H I, optical, and radio continuum morphology consistent with thehypothesis that ram pressure, along with H I ablation, could producemajor morphological disturbances as well as enhancements in the diffusesynchrotron emission due to magnetic field compression.
|Northern dwarf and low surface brightness galaxies. II - The Green Bank neutral hydrogen survey|
The paper reports neutral hydrogen observations of a large sample ofdwarf and other low surface brightness galaxies. A detailed discussionand error analysis of the observations are presented, and spectra aredisplayed for 329 galaxies detected for the first time, or detected withsubstantially better signal-to-noise ratios than achieved previously.The positions on the sky of 667 galaxies meeting the present selectioncriteria north of delta = 38 deg are shown. The distribution of theredshifts of galaxies detected at Green Bank is illustrated. The GreenBank detections tapered off strongly below the median H I flux of 3.7 Jykm/s detected at Arecibo: only 12 percent of the Green Bank sample wasdetected with smaller fluxes.
|Nearby galaxies. I - The catalogue|
The data of 289 nearby galaxies have been compiled. The inclusion of agalaxy into the catalog depends on its redshift as in the catalogue ofKraan-Korteweg and Tammann (1979) or on the fact that the objects areknown to be certain or probable members of nearby groups. The galaxiesin the sample form the Local Group with 51 certain and probable membersand several additional groups. One third of the galaxies in the catalog(96 objects) does not seem to belong to any group. The main emphasis isto get a distance-limited sample of galaxies, especially of dwarfobjects.
|21 centimeter study of spiral galaxies in the Coma supercluster. II - Evidence for ongoing gas stripping in five cluster galaxies|
High-sensitivity 21 cm observations of 73 galaxies in the Comasupercluster are presented. Seventeen new redshifts are reported. Threegalaxies in A1367 and two in the Coma Cluster are found with remarkablyasymmetrical H I spectra indicating uneven gas distribution in theirdisks. This unstable configuration is interpreted as being due toongoing dynamical gas stripping taking place on time scales shorter thanthose required for differential rotation to redistribute the gas, i.e.,a few times 100 million yr. This suggests that spiral galaxies arecontinuously supplied to the clusters from the surrounding supercluster.
|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.
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