Contents
Images
Upload your image
DSS Images Other Images
Related articles
The Environmental Influence on the Evolution of Local Galaxies
The results of an Hα photometric survey of 30 dwarf galaxies ofvarious morphologies in the Centaurus A and Sculptor groups arepresented. Of these 30, emission was detected in 13: eight are oflate-type, two are early-type, and three are of mixed morphologies. Thetypical flux detection limit of ~2 × 10–16 ergs–1 cm–2 translates into astar-formation rate (SFR) detection limit of 4 ×10–6 M sun yr–1. In lightof these results, the morphology-density relation is re-examined, and itis shown that, despite a number of unaccounted parameters, there aresignificant correlations between the factors determining themorphological type of a galaxy and its environment. Dwarf galaxies inhigh-density regions have a lower current SFR and lower neutral gascontent than their low-density counterparts, confirming earlier resultsfrom the Local Group and other denser environments. The effect ofenvironment is also seen in the timescale formed from the ratio of blueluminosity to current SFR—dwarfs in higher-density environmentshave larger values, indicating relatively higher past average SFR. Theinfluence of environment extends very far, and no dwarfs from our samplecan be identified as "field" objects.
| Deep Near-Infrared Surface Photometry of 57 Galaxies in the Local Sphere of Influence
We present H-band (1.65 μm) surface photometry of 57 galaxies drawnfrom the Local Sphere of Influence (LSI), with distances of less than 10Mpc from the Milky Way. The images, with a typical surface brightnesslimit 4 mag fainter than the Two Micron All Sky Survey (2MASS) (24.5 magarcsec–2 < μlim < 26 magarcsec–2), have been obtained with the Infrared Imagerand Spectrograph 2 on the 3.9 m Anglo-Australian Telescope. A total of22 galaxies that remained previously undetected in the near-infrared(NIR), and potentially could have been genuinely young galaxies, werefound to have an old stellar population with a star density 1-2 magbelow the 2MASS detection threshold. The cleaned NIR images reveal themorphology and extent of many of the galaxies for the first time. Forall program galaxies, we derive radial luminosity profiles,ellipticities, and position angles, together with global parameters suchas total magnitude, mean effective surface brightness, and half-lightradius. Our results show that 2MASS underestimates the total magnitudeof galaxies with langμ H rangeff between 18 and21 mag arcsec–2 by up to 2.5 mag. The Sérsicparameters that best describe the observed surface brightness profilesare also presented. By adopting accurate galaxy distances and an H-bandmass-to-light ratio of Upsilon H * = 1.0 ±0.4, the LSI galaxies are found to cover a stellar-mass range of5.6<\log _{10}(\mathcal{M}_stars). The results are discussed alongwith previously obtained optical data. Our sample of low-luminositygalaxies is found to closely follow the optical-infrared B-versus-Hluminosity relation defined by brighter galaxies, with a slope of 1.14± 0.02 and a scatter of 0.3 mag. Finally, we analyze theluminosity-surface brightness relation to determine an empiricalmass-to-light ratio of Upsilon H * = 0.78± 0.08 for late-type galaxies in the H band.
| Photometric properties of the Local Volume dwarf galaxies
We present surface photometry and metallicity measurements for 104nearby dwarf galaxies imaged with the Advanced Camera for Surveys andWide Field and Planetary Camera 2 aboard the Hubble Space Telescope. Inaddition, we carried out photometry for 26 galaxies of the sample andfor Sextans B on images of the Sloan Digital Sky Survey. Our samplecomprises dwarf spheroidal, irregular and transition type galaxieslocated within ~10 Mpc in the field and in nearby groups: M81, CentaurusA, Sculptor and Canes Venatici I cloud. It is found that the early-typegalaxies have on average higher metallicity at a given luminosity incomparison to the late-type objects. Dwarf galaxies with MB>= -12 to -13 mag deviate towards larger scalelengths from thescalelength-luminosity relation common for spiral galaxies, h ~L0.5B. The following correlations betweenfundamental parameters of the galaxies are consistent with expectationsif there is pronounced gas loss through galactic winds: (1) between theluminosity of early-type dwarf galaxies and the mean metallicity ofconstituent red giant branch stars, Z ~ L0.4, (2) betweenmean surface brightness within the 25 magarcsec-2 isophoteand the corresponding absolute magnitude in the V and I bands, SB25 ~ 0.3M25 and (3) between the central surfacebrightness (or effective surface brightness) and integrated absolutemagnitude of galaxies in the V and I bands, SB0 ~0.5ML,SB e ~ 0.5 Me. The knowledge ofbasic photometric parameters for a large sample of dwarf galaxies isessential for a better understanding of their evolution.Based on observations with the NASA/ESA Hubble Space Telescope, obtainedat the Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy (AURA), Inc.,under NASA contract NAS 5-26555.E-mail: sme@sao.ru
| Neutral Hydrogen Clouds Near Early-Type Dwarf Galaxies of the Local Group
Parkes neutral hydrogen 21 cm line (H I) observations of thesurroundings of nine early-type Local Group dwarfs are presented. Wedetected numerous H I clouds in the general direction of those dwarfs,and these clouds are often offset from the optical center of thegalaxies. Although all the observed dwarfs, except Antlia, occupyphase-space regions where the high-velocity cloud (HVC) density is wellabove average, the measured offsets are smaller than one would expectfrom a fully random cloud distribution. Possible association is detectedfor 11 of the 16 investigated clouds, while for two galaxies, Sextansand Leo I, no H I was detected. The galaxies in which H I clouds werefound not to coincide with the optical yet have a significantprobability of being associated are the Sculptor dwarf, Tucana, LGS 3,Cetus, and Fornax. If the clouds are indeed associated, these galaxieshave H I masses of MHI=2×105,2×106, 7×105, 7×105,and 1×105 Msolar, respectively. However,neither ram pressure nor tidal stripping can easily explain the offsets.In some cases, large offsets are found where ram pressure should be theleast effective.
| H I Detection of Two Dwarf S0 Galaxies in Nearby Groups: ESO 384-016 and NGC 59
A H I survey of 10 dE/dS0 galaxies in the nearby Sculptor and CentaurusA groups was made using the Australia Telescope Compact Array. Theobserved galaxies have accurate distances derived by Jerjen et al. usingthe surface brightness fluctuation technique. Their absolute magnitudesare in the range -9.5>MB>-15.3. Only two of the 10galaxies were detected at our detection limit (~1.0×106Msolar for the Centaurus group and ~5.3×105Msolar for the Sculptor group): the two dS0 galaxies ESO384-016 in the Centaurus A group and NGC 59 in the Sculptor group, withH I masses of (6.0+/-0.5)×106 and(1.4+/-0.1)×107 Msolar, respectively. Thosetwo detections were confirmed using the Green Bank Telescope. Thesesmall H I reservoirs could fuel future generations of low-level starformation and could explain the bluer colors seen at the center of thedetected galaxies. Similar to what is seen with the Virgo dwarfellipticalss, the two objects with H I appear to be on the outskirts ofthe groups.
| Globular Clusters in Dwarf Galaxies
Data are currently available on the luminosities and half-light radii of101 globular clusters associated with low-luminosity parent galaxies.The luminosity distribution of globular clusters embedded in dwarfgalaxies having Mv>-16 is found to differ dramaticallyfrom that for globular clusters surrounding giant host galaxies withMv<-16. The luminosity distribution of globular clustersin giant galaxies peaks at Mv~-7.5, whereas that for dwarfgalaxies is found to increase monotonically down to the completenesslimit of the cluster data at Mv~-5.0. Unexpectedly, thepower-law distribution of the luminosities of globular clusters hostedby dwarf galaxies is seen to be much flatter than that of the bright,unevolved part of the luminosity distribution of globular clustersassociated with giant galaxies. The specific frequency of globularclusters fainter than Mv=-7.5 is found to be particularlyhigh in dwarf galaxies. The luminosity distribution of the LMC globularclusters is similar to that found in giant galaxies and differs fromthose of globular clusters in dwarf galaxies. The present data appear toshow no strong dependence of globular cluster luminosity on themorphological type of their parent galaxies. No attempt is made toexplain the unexpected discovery that the luminosity distribution ofglobular clusters is critically dependent on parent galaxy luminosity(or mass) but insensitive to the morphological type of the host galaxy.
| Detection of Neutral Hydrogen in Early-Type Dwarf Galaxies of the Sculptor Group
We present results of deep 21 cm neutral hydrogen (H I) lineobservations of five early- and mixed-type dwarf galaxies in the nearbySculptor group using the Australia Telescope National Facility 64 mParkes Radio Telescope. Four of these objects, ESO 294-G010, 410-G005,540-G030, and 540-G032, were detected in H I with neutral hydrogenmasses in the range (2-9)×105 Msolar(MHI/LB=0.08, 0.13, 0.16, and 0.18Msolar L-1solar, respectively). These HI masses are consistent with the gas mass expected from stellar outflowsover a large period of time. Higher spatial resolution H I data from theAustralia Telescope Compact Array interferometer were further analyzedto measure more accurate positions and the distribution of the H I gas.In the cases of the dwarfs ESO 294-G010 and ESO 540-G030, we findsignificant offsets of 290 and 460 pc, respectively, between theposition of the H I peak flux and the center of the stellar component.These offsets are likely to have internal causes such as the winds fromstar-forming regions. The fifth object, the spatially isolated dwarfelliptical galaxy Scl-dE1, remains undetected at our 3 σ limit of22.5 mJy km s-1 and thus must contain less than105 Msolar of neutral hydrogen. This leavesScl-dE1 as the only Sculptor group galaxy known in which no interstellarmedium has been found to date. The object joins a list of similarsystems, including the Local Group dwarfs Tucana and Cetus, that do notfit into the global picture of the morphology-density relation in whichgas-rich dwarf irregular galaxies are in relative isolation andgas-deficient dwarf elliptical galaxies are satellites of more luminousgalaxies.
| Hubble Space Telescope imaging of globular cluster candidates in low surface brightness dwarf galaxies
Fifty-seven nearby low surface brightness dwarf galaxies (-10MV -16) were searched for globular cluster candidates(GCCs) using Hubble Space Telescope WFPC2 imaging in V and I. The sampleconsists of 18 dwarf spheroidal (dSph), 36 irregular (dIrr), and 3"transition" type (dIrr/dSph) galaxies with angular sizes less than 3.7kpc situated at distances 2{-}6 Mpc in the field and in the nearbygroups: M 81, Centaurus A, Sculptor, Canes Venatici I cloud. We findthat 50% of dSph, dIrr/dSph, and dIrr galaxies contain GCCs. Thefraction of GCCs located near the center of dwarf spheroidal galaxies is2 times higher than for dIrrs. The mean integral color of GCCs indSphs, (V-I)_0=1.04±0.16 mag, coincides with the correspondingvalue for Galactic globular clusters and is similar to the blue globularcluster sub-populations in massive early-type galaxies. The colordistribution for GCCs in dIrrs shows a clear bimodality with peaks near(V-I)0 = 0.5 and 1.0 mag. Blue GCCs are presumably young withages t1 Gyr, while the red GCC population is likely to be older.The detected GCCs have absolute visual magnitudes betweenMV=-10 and -5 mag. We find indications for an excesspopulation of faint GCCs with MV-6.5 mag in both dSphand dIrr galaxies, reminiscent of excess populations of faint globularclusters in nearby Local Group spiral galaxies. The measurement ofstructural parameters using King-profile fitting reveals that most GCCshave structural parameters similar to extended outer halo globularclusters in the Milky Way and M 31, as well as the recently discoveredpopulation of "faint fuzzy" clusters in nearby lenticular galaxies.
| The Local Group and Other Neighboring Galaxy Groups
Over the last few years, rapid progress has been made in distancemeasurements for nearby galaxies based on the magnitude of stars on thetip of the red giant branch. Current CCD surveys with the Hubble SpaceTelescope (HST) and large ground-based telescopes bring ~10% accuratedistances for roughly a hundred galaxies within 5 Mpc. The new data ondistances to galaxies situated in (and around) the nearest groups-theLocal Group, M81 Group, Cen A/M83 Group, IC 342/Maffei Group, Sculptorfilament, and Canes Venatici cloud-allowed us to determine their totalmass from the radius of the zero-velocity surface, R0, whichseparates a group as bound against the homogeneous cosmic expansion. Thevalues of R0 for the virialized groups turn out to be closeeach other, in the range of 0.9-1.3 Mpc. As a result, the total massesof the groups are close to each other, as well, yielding total mass toblue luminosity ratios of 10-40 MsolarL-1solar. The new total mass estimates are 3-5times lower than old virial mass estimates of these groups. Becauseabout half of galaxies in the Local volume belong to such loose groups,the revision of the amount of dark matter (DM) leads to a low localdensity of matter, Ωm~=0.04, which is comparable withthe global baryonic fraction Ωb but much lower than theglobal density of matter, Ωm=0.27. To remove thediscrepancy between the global and local quantities ofΩm, we assume the existence of two different DMcomponents: (1) compact dark halos around individual galaxies and (2) anonbaryonic dark matter ``ocean'' with ΩDM1~=0.07 andΩDM2~=0.20, respectively.Based in part on observations made with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS 5-26555.
| 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.
| Distances to nearby galaxies in Sculptor
We present an analysis of Hubble Space Telescope/WFPC2 images of ninenearby galaxies in Sculptor. We derive their distances from theluminosity of the tip of the red giant branch stars with a typicalaccuracy of ~ 12%. Their distances are 4.21 Mpc (Sc 22), 4.92 Mpc (DDO226), 3.94 Mpc (NGC 253), 3.40 Mpc (KDG 2), 3.34 Mpc (DDO 6), 3.42 Mpc(ESO 540-030), 4.43 Mpc (ESO 245-05), 4.27 Mpc (UGCA 442), and 3.91 Mpc(NGC 7793). The galaxies are concentrated in several spatially separatedloose groups around NGC 300, NGC 253, and NGC 7793. The Sculptor galaxycomplex together with the CVn I cloud and the Local Group form a 10 Mpcfilament, apparently driven by the free Hubble flow.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.
| Star Formation in Sculptor Group Dwarf Irregular Galaxies and the Nature of ``Transition'' Galaxies
We present new Hα narrowband imaging of the H II regions in eightSculptor group dwarf irregular (dI) galaxies. The Hα luminositiesof the detected H II regions range from some of the faintest detected inextragalactic H II regions (~1035 ergs s-1 in SC24) to some of the most luminous (~1040 ergs s-1in NGC 625). The total Hα luminosities are converted into currentstar formation rates (SFRs). Comparing the Sculptor group dI's to theLocal Group dI's, we find that the Sculptor group dI's have, on average,lower values of SFR when normalized to either galaxy luminosity or gasmass (although there is considerable overlap between the two samples).The range for both the Sculptor group and Local Group samples is largewhen compared with that seen for the sample of gas-rich, quiescent, lowsurface brightness (LSB) dI's from van Zee et al. (published in 1997)and the sample of isolated dI's from van Zee (from 2000 and 2001). Thisis probably best understood as a selection effect since the nearby groupsamples have a much larger fraction of extremely low luminosity galaxiesand the smaller galaxies are much more liable to large relativevariations in current SFRs. The Sculptor group and LSB samples are verysimilar with regard to mean values of both τgas andτform, and the Local Group and isolated dI samples arealso similar to each other in these two quantities. Currently, theSculptor group lacks dI galaxies with elevated normalized current SFRsas high as the Local Group dI's IC 10 and GR 8. The properties of``transition'' (dSph/dIrr) galaxies in Sculptor and the Local Group arealso compared and found to be similar. The transition galaxies aretypically among the lowest luminosities of the gas-rich dwarf galaxies.Relative to the dwarf irregular galaxies, the transition galaxies arefound preferentially nearer to spiral galaxies and are found nearer tothe center of the mass distribution in the local cloud. While most ofthese systems are consistent with normal dI galaxies, exhibitingtemporarily interrupted star formation, the observed density-morphologyrelationship (which is weaker than that observed for the dwarfspheroidal galaxies) indicates that environmental processes such as``tidal stirring'' may play a role in causing their lower SFRs.
| Tip of the red giant branch distance for the Sculptor group dwarf ESO 540-032
We present the first VI CCD photometry for the Sculptor group galaxy ESO540-032 obtained at the Very Large Telescope UT1+FORS1. The (I, V-I)colour-magnitude diagram indicates that this intermediate-type dwarfgalaxy is dominated by old, metal-poor ([Fe/H]~ -1.7 dex) stars, with asmall population of slightly more metal-rich ([Fe/H]~ -1.3 dex), young(age 150-500 Myr) stars. A discontinuity in the I-band luminosityfunction is detected at I0 = 23.44+/- 0.09 mag. Interpretingthis feature as the tip of the red giant branch and adoptingMI = -4.20+/- 0.10 mag for its absolute magnitude, we havedetermined a Population II distance modulus of (m - M)0 =27.64 +/- 0.14 mag (3.4 +/- 0.2 Mpc). This distance confirms ESO 540-032as a member of the nearby Sculptor group but is significantly largerthan a previously reported value based on the Surface BrightnessFluctuation (SBF) method. The results from stellar population synthesismodels suggest that the application of the SBF technique on dwarfgalaxies with mixed morphology requires a detailed knowledge of theunderlying stellar composition and thus offers no advantage over adirect distance measurement using the tip of the red giant branch asdistance indicator. We produce the surface brightness profiles for ESO540-032 and derive the photometric and structural parameters. The globalproperties follow closely the relations between metallicity and bothabsolute magnitude and central surface brightness defined by dwarfelliptical galaxies in the Local Group. Finally, we identify and discussa non-stellar object near the galaxy center which may resemble aglobular cluster. Based on observations collected at the EuropeanSouthern Observatory (ESO 64.N-0069).
| Hubble Space Telescope Photometry of the Dwarf Spheroidal Galaxy ESO 410-G005
We present Hubble Space Telescope WFPC2 imaging of the nearby lowsurface brightness dwarf spheroidal galaxy ESO 410-G005, which has beenresolved into stars for the first time. The resulting color-magnitudediagram for about 2500 stars shows a red giant branch with a tip atI=22.4+/-0.15 mag, which yields a distance of DMW=1.9+/-0.2Mpc. ESO 410-G005 is found to be metal-poor with a mean metallicity of<[Fe/H]>=(-1.8+/-0.4) dex estimated from its red giant branch.Upper asymptotic giant branch stars appear to be present near the centerof the galaxy, indicative of a substantial, centrally concentratedintermediate-age population, unless these objects are artifacts ofcrowding. Previous studies did not detect ESO 410-G005 in Hα or inH I. Based on our distance estimate, ESO 410-G005 is a probable memberof the Sculptor group of galaxies. Its linear separation from thenearest spiral, NGC 55, is 230 kpc on the sky. The deprojectedseparation ranges from 340 to 615 kpc depending on the assumed distanceof NGC 55. The deprojected distance from the Sculptor group spiral NGC300 is (385+/-200) kpc. ESO 410-G005 appears to be a relatively isolateddSph within the Sculptor group. Its absolute magnitude,MV,0=-12.1+/-0.2 mag, its central surface brightness,μV,0=22.7+/-0.1 mag arcsec-2, and its meanmetallicity, [Fe/H]=(-1.8+/-0.4) dex follow the trend observed for dwarfgalaxies in the Local Group. Based on observations made with theNASA/ESA Hubble Space Telescope. The Space Telescope Science Instituteis operated by the Association of Universities for Research inAstronomy, Inc., under NASA contract NAS 5-26555.
| Surface BR Photometry of Newly Discovered Dwarf Elliptical Galaxies in the Nearby Sculptor and Centaurus A Groups
Prompted by the recent finding of a large number of gas-rich dwarfirregular galaxies in the nearby southern galaxy groups Sculptor (Scl)and Centaurus A (Cen A) we carried out a complementary survey to searchfor members of the gas-poor dwarf elliptical (dE) galaxy family. Intotal 18 dE candidates were identified on SRC Sky Survey films coveringthe group regions. For five dE's in the Scl group and five in the Cen Agroup, membership information is available from surface brightnessfluctuations distance measurements; two dEs in each group also haveindependent redshift measurements. The remaining eight galaxies havebeen associated to the groups based on their morphology. We acquireddeep B- and R-band CCD images for all galaxies and determined theirphotometric and structural parameters. According to the magnitude rangecovered, -14
| HI observations of nearby galaxies . I. The first list of the Karachentsev catalog
We present HI observations of the galaxies in the first list of theKarachentsev catalog of previously unknown nearby dwarf galaxies(Karachentseva & Karachentsev 1998). This survey covers all knownnearby galaxy groups within the Local Volume (i.e. within 10 Mpc) andtheir environment, that is about 25% of the total sky. A total of 257galaxies have been observed with a detection rate of 60%. We searched afrequency band corresponding to heliocentric radial velocities from -470km s-1 to ~ +4000 km s-1. Non-detections areeither due to limited coverage in radial velocity, confusion with LocalHI (mainly in the velocity range -140 km s-1 to +20 kms-1), or lack of sensitivity for very weak emission. 25% ofthe detected galaxies are located within the Local Volume. Thosegalaxies are dwarf galaxies judged by their optical linear diameter (1.4+/- 0.2 kpc on the average), their mean total HI mass (4.6107 Msun), and their observed linewidths (39 kms-1).
| 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 130.79.128.5 orhttp//cdsweb.u-strasbg.fr/Abstract.html
| Surface Brightness Fluctuation Distances to Dwarf Elliptical Galaxies in the Sculptor Group
As part of an ongoing search for dwarf elliptical galaxies (dE's) in thevicinity of the Local Group (Jerjen et al.), we acquired deep B- andR-band images for five dE candidates identified on morphologicalcriteria in the Sculptor (Scl) group region. We carried out a surfacebrightness fluctuation (SBF) analysis on the R-band images to measurethe apparent fluctuation magnitude m_R for each dE. Using predictionsfrom stellar population synthesis models (Worthey) giving M_R values inthe narrow range between -1.17 and -1.13, the galaxy distances weredetermined. All of these dE candidates turned out to be satellites ofScl group major members. A redshift measurement of the dE candidate ESO294-010 yielded an independent confirmation of its group membership: the[O III] and Hα emission lines from a small H II region gave aheliocentric velocity of 117 (+/-5) km s^-1, in close agreement with thevelocity of its parent galaxy NGC 55 (v_ȯ = 125 km s^-1). Theprecision of the SBF distances (5%-10%) contributes to delineating thecigar-like distribution of the Scl group members, which extend overdistances from 1.7 to 4.4 Mpc and are concentrated in three, possiblyfour subclumps. The Hubble diagram for nine Scl galaxies, including twoof our dE's, exhibits a tight linear velocity-distance relation with asteep slope of 119 km s^-1 Mpc^-1. The results indicate thatgravitational interaction among the Scl group members plays only a minorrole in the dynamics of the group. However, the Hubble flow of theentire system appears strongly disturbed by the large masses of ourGalaxy and M31, which leads to the observed shearing motion. From thedistances and velocities of 49 galaxies located in the Local Group andtoward the Scl group, we illustrate the continuity of the galaxydistribution, which strongly supports the view that the two groups forma single supergalactic structure.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| A list of new nearby dwarf galaxy candidates
To increase completeness of the distance limited sample of nearbygalaxies from the \cite[Kraan-Korteweg & Tammann (1979)]{Kra79}catalogue we undertook a search for small companions of larger knowngalaxies which have corrected radial velocities within 500 km/s. Basedprimarily on the POSS-II and ESO/SERC films we found 260 nearby dwarfgalaxy candidates with angular diameters aga0 .5 arcmin. More than 50%of the objects were revealed for the first time. As we suppose, asignificant part of them (about 30%) may really belong to the LocalVolume sample. Tables 1 and 2 also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via\breakftp://cdsweb.u-strasbg.fr/Abstract.html
| Discovery of Numerous Dwarf Galaxies in the Two Nearest Groups of Galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1313C&db_key=AST
| 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.
| Observations of southern dwarf galaxies
Here we present the results of neutral hydrogen observations of dwarfgalaxies in the Southern Hemisphere. About half of the 88 objectsobserved are galaxies selected, but optically undetected, for theSouthern Sky Redshift Survey. The remaining objects are smallergalaxies, down to the 1 arcmin diameter limit of the ESO catalog, in thesouthern and northern galactic caps.
| Southern Sky Redshift Survey - The catalog
The catalog of radial velocities for galaxies which comprise thediameter-limited sample of the Southern Sky Redshift Survey ispresented. It consolidates the data of observations carried out at theLas Campanas Observatory, Observatorio Nacional, and South AfricanAstronomical Observatory. The criteria used for the sample selection aredescribed, as well as the observational procedures and the techniqueutilized to obtain the final radial velocities. The intercomparisonbetween radial velocity measurements from different telescopes indicatesthat the final data base is fairly homogeneous with a typical error ofabout 40 km/s. The sample is at present 90 percent complete, and themissing galaxies are predominantly objects with very low surfacebrightness for which it is very difficult to obtain optical redshifts.
| An HI survey of late-type galaxies in the Southern Hemisphere. I - The SGC sample
The present H I survey of Southern Hemisphere late-type galaxies wascompleted at the Nancay radio telescope between 1985 and 1988 and coverslarge galaxies selected from the Corwin et al. (1985) SGC catalog. Ofthe 311 galaxies observed, only 245 were detected due to the very lowsurface brightness of the Magellanic irregulars. These determinationsare conceived as useful for the establishment of distance criteria forlate-type galaxies. A histogram is presented of the velocities for thedetected galaxies vs morphological stages; attention is given toindividual spectra for 242 galaxies in the sample.
| A catalogue of dwarf galaxies south of delta = -17.5 deg
A catalog of 584 suspected dwarf galaxies south of declination -17.5 degis presented. The survey was done on ESO(B) and SRC(J) plates and films.Position, major and minor axes, luminosity classes, and types(irregular, spiral, elliptical) are given.
| Southern Galaxy Catalogue.
Not Available
| The distribution of Sculptor-type dwarf galaxies.
Not Available
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
