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|Australia Telescope Compact Array H I observations of the NGC 6845 galaxy group|
We present the results of Australia Telescope Compact Array (ATCA) HIline and 20-cm radio continuum observations of the galaxy quartet NGC6845. The HI emission extends over all four galaxies but can only beassociated clearly with the two spiral galaxies, NGC 6845A and B, whichshow signs of strong tidal interaction. We derive a total HI mass of atleast 1.8 × 1010 Msolar, most of which isassociated with NGC 6845A, the largest galaxy of the group. Weinvestigate the tidal interaction between NGC 6845A and B by studyingthe kinematics of distinct HI components and their relation to the knownHII regions. No HI emission is detected from the two lenticulargalaxies, NGC 6845C and D. A previously uncatalogued dwarf galaxy, ATCAJ2001-4659, was detected 4.4 arcmin NE from NGC 6845B and has an HI massof ~5 × 108 Msolar. No HI bridge is visiblebetween the group and its newly detected companion. Extended 20-cm radiocontinuum emission is detected in NGC 6845A and B as well as in thetidal bridge between the two galaxies. We derive star formation rates of15-40 Msolar yr-1.
|FAUST observations in the Fourth Galactic Quadrant*|
We analyse UV observations with FAUST of four sky fields in the generaldirection of the Fourth Galactic Quadrant, in which we detect 777 UVsources. This is ~50 per cent more than detected originally by Bowyer etal. We discuss the source detection process and the identification of UVsources with optical counterparts. For the first time in this project weuse ground-based objective-prism information for two of the fields, toselect the best-matching optical objects with which to identify the UVsources. Using this, and correlations with existing catalogues, wepresent reliable identifications for ~75 per cent of the sources. Mostof the remaining sources have assigned optical counterparts but, lackingadditional information, we offer only plausible identifications. Wediscuss the types of objects found, and compare the observed populationwith predictions of our UV Galaxy model.
|Southern Isolated Galaxy Triplets|
Seventy-six isolated triple systems of galaxies with declinatiosnδ<-3° were selected using ESO/SERC and POSS-I sky surveydata. The equatorial coordinates, configuration types, angular sizes,component angular separations, component morphological types, totalmagnitudes, and other parameters are reported for each triplet.Radial-velocity estimates are available for all components in 33 of the76 triplets. The median values of the main dynamicalparametersradial-velocity dispersion, mean harmonic radius,absolute magnitudes of member galaxies, and mass-to-luminosityratiosare similar to those obtained earlier for 83 isolatedtriple systems with δ>-3°.
|Study of the Interacting System NGC 6845|
We present optical spectroscopy, B, V, R, and I CCD photometry, and VLAneutral hydrogen observations of the interacting quartet NGC 6845, alsoknow as Klemola 30. NGC 6845 A, the dominant component, sports a broadand bright tidal bridge and a faint tidal tail, which bifurcates. Thetidal bridge has a B-I color bluer than that of the inner disk of NGC6845 A. Five strong condensations, identified as H II regions brighterthan the brightest one known in our Galaxy, are found along the tidalbridge, with the two most luminous located at the bridge tip. Two giantH II regions, comparable to 30 Dor, are located where the tidal bridgeand the tidal tail join the disk of NGC 6845 A. Since the age of the HII regions is 3-8 Myr, star formation continued to occur along the tidalbridge and in the tidal arm well after they began to be torn apart(>=100 Myr). Satoh model fitting to the optical rotation curve of theA component reveals a kinematical mass of (4.4+/-1.2)x10^11 M_solar,inside the central 12 kpc (H_0=75 km s^-1 Mpc^-1). The H I emissionconsist of two components, a more massive one that belongs to NGC 6845 Aand a second one associated with NGC 6845 B. We do not detect gasassociated with galaxies C and D. The total amount of H I is 1.4x10^10M_solar, 5 time higher than the H I content of the Milky Way. The H Ikinematics indicates an amount of dark matter associated with the Acomponent 2 times higher than the mass inside its central 12 kpc. Thegroup kinematics indicates M/L~43(+/-2)(M/L)_solar orM/L~66(+/-2)(M/L)_solar, according to two different prescriptions forthe internal absorption correction. In spite of this large difference,both values furnish a similar group mass (~1x10^13 M_solar). Althoughpreliminary results on N-body simulations indicate that either B or Cmight well create a tidal feature like the bridge of the A component,the collision with B appears to be more favorable.
|A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1|
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
|Revised coordinates for 373 selected objects in the Southern Galaxy Catalogue|
Improved positions have been determined for 373 galaxies listed in theSouthern Galaxy Catalogue of Corwin et al. (1985) as having poorcoordinates. The revised coordinates are expected to be good to 6 arcsec(rms) in each coordinate.
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