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Extended very cold dust in the interacting HI ring galaxy pair NGC 2293 / 2292
The LGG 138 galaxy group members NGC 2292 and NGC 2293 were imaged withISOPHOT in the far-infrared (FIR) at {60 μ m}, {100 μ m}, and {200μ m}. While no FIR emission is seen at {60 μ m}, and only very lowlevel emission is present at {100 μ m}, compact FIR emission fromboth NGC 2292 and NGC 2293 galaxy centres and extended emission likelyassociated with tidally removed dust and the HI ring surrounding NGC2292 / 2293 is strongly detected at {200 μ m}. Additionally, acompact FIR source associated with the neighbouring galaxy NGC 2295 isstrongly detected at {200 μ m}. Remarkably, none of these threegalaxies have been detected individually in 21 cm HI emission. Thesteeply rising far-infrared spectral energy distribution of theapparently interacting NGC 2292 / 2293 pair towards longer wavelengthsindicates the thermal emission of very cold dust with a temperature of13 K, much lower than typical values of interacting systems or evenquiescent spiral galaxies. The FIR data of this galaxy group clearlyshows for the first time that there could be FIR dust emission notaccompanied by HI, that dust even in an interacting system can have avery low dust temperature, and furthermore that gravitationalinteraction can give rise to an extended diffuse dust distribution.
| A study of neutral hydrogen in five small galaxy groups
High-resolution Hi imaging observations of a heterogeneous sample ofsmall galaxy groups are presented. The five galaxy groups studied show abroad range of individual Hi properties: e.g. loose groups surroundingLGG 138 and the genuinely compact LGG 455 are identified; a massive ringof neutral gas is discovered encircling two luminous galaxies in the LGG138 group; a galaxy-sized mass of Hi is found in LGG 455 confined to anextragalactic cloud which exceeds the threshold density for starformation, yet is optically invisible; and the CCG 1 group is argued tobe a chance alignment of Centaurus cluster galaxies. Global results ofthe study are that the deficit of Hi flux in synthesis imaging datacompared with single-dish data is put forward as a quantitative measureof the diffuseness of neutral gas in galaxy groups; several groupscontain gas-poor galaxies that ordinarily would contain detectablequantities of Hi - this is interpreted as being caused by an increasedchance of gas-sweeping collisions in the group environment; and someevidence is found to support previous findings that compact groupspreferentially occur in loose systems.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A new HI ring: LGG 138
A complete ring of neutral hydrogen gas (HI) in the LGG 138 group ofgalaxies has been found. The HI mass of the ring is greater than 10^9solar masses, and the gas appears to be rotating with a projectedcircular speed of about 200 km per sec. Two bright galaxies are enclosedby the ring, both having radial velocities consistent with membership ofthe group. Faint stellar emission extends to the radial distance of theHI ring, where a small but distinct colour discontinuity of between 0.05and 0.20 magnitudes is detected. Three simple models for the formationof the system are briefly described, the most likely appearing to be apast gas-sweeping collision between one of the two bright galaxies andan outside intruder, with the colour break being partly due to anexpanding density wave that is triggering star formation, and partly toa different stellar population that has been collected from theoutskirts of the intruder.
| Compact groups of galaxies in the nearby universe
We have searched for compact groups of galaxies among the largestcatalog of nearby groups (LGG catalog). 21 new compact groups of atleast 3 members were found. Their surface brightnesses are generallylower than those of Hickson compact groups (HCGs), and theircharacteristics are close to those of loose groups. We have alsoretrieved all HCGs of the nearby universe. These are all embedded ingroups, forming the cores or substructures of loose groups. Theseresults suggest that compact groups may form as core or substructureswithin loose groups (like the HCGs), or form from loose groups when theystart collapsing (like those of the LGG).
| Observational data for the kinematics of the local universe. I - Radial velocity measurements
The study of the local velocity field requires the use of a very largesample to describe as accurately as possible some prominent features ofthe local kinematics. The problem of collecting a large sample is mademore difficult because of the Malmquist bias which plagues distancedeterminations. The present program aims at determining bias-freedistances for a complete sample in order to study the local velocityfield. The present paper gives 303 preliminary optical and radioredshifts measured for this program at ESO, OHP and NancayObservatories.
| The luminosity distributions of edge-on spiral and lenticular galaxies. II - Modelling the non-thin disc light in a sample of ten galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990MNRAS.242...59S&db_key=AST
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