Showing papers by "Bärbel S. Koribalski published in 2003"
TL;DR: In this article, the authors measured 21-cm absorption spectra in the direction of three southern pulsars, PSRs B0736-40, B1451-68 and B1641-45, in three separate epochs spread over 2.5 yr.
Abstract: We have measured 21-cm absorption spectra in the direction of three southern pulsars, PSRs B0736-40, B1451-68 and B1641-45, in three separate epochs spread over 2.5 yr. We see no evidence for any changes in the absorption spectra over this time span in spite of good velocity resolution and sensitivity. Towards PSR B1641-45 we place an upper limit of 10 1 9 cm - 2 on the change in the column density of the cold, neutral gas. In addition, we observed PSR B 1557-50 and compared its HI absorption spectrum with spectra taken in 1980 and 1994. A prominent deep absorption feature seen at -110 km s - 1 in 1994 is weaker in 2000 and likely was not present at all in 1980. Using the standard interpretation which links the distance traversed by the pulsar to a physical cloud size, this results in a cloud size of ∼1000 au and density of 2 x 10 4 cm - 3 , parameters typical of those seen in other observations. These results are also consistent with an alternative model by Deshpande who expects the largest variations in optical depth to be seen against the longest time intervals.
42 citations
TL;DR: In this paper, the authors detected a large H I cloud between IC 2554 and the elliptical galaxy NGC 3136B, which is sometimes described as a colliding pair.
Abstract: ATCA H I and radio continuum observations of the peculiar southern galaxy IC 2554 and its surroundings reveal typical signatures of an interacting galaxy group We detected a large H I cloud between IC 2554 and the elliptical galaxy NGC 3136B The gas dynamics in IC 2554 itself, which is sometimes described as a colliding pair, are surprisingly regular, whereas NGC 3136B was not detected The H I cloud, which emerges from IC 2554 as a large arc-shaped plume, has a size of similar to30 kpc, larger than that of IC 2554 The total H I mass of the IC 2554 system is similar to2 x 10(9) M, one-third of which resides in the H I cloud It is possible that tidal interaction between IC 2554 and NGC 3136B caused this spectacular H I cloud, but the possibility of IC 2554 being a merger remnant is also discussed We also detected H I gas in the nearby galaxies ESO 092-G009 and RKK 1959 and an associated H I cloud, ATCA J1006-6710 Together they have an H I mass of similar to46 x 10(8) M- Another new H I source, ATCA J1007-6659, with an H I mass of only similar to22 x 10(7) M was detected roughly between IC 2554 and ESO 092-G009 and corresponds to a face-on low surface brightness dwarf galaxy Star formation is evident only in the galaxy IC 2554 with a rate of similar to4 M yr(-1)
19 citations
TL;DR: In this paper, the authors present the results of Australia Telescope Compact Array (ATCA) H i line and 20-cm radio continuum observations of the galaxy quartet NGC 6845.
Abstract: We present the results of Australia Telescope Compact Array (ATCA) H i line and 20-cm radio continuum observations of the galaxy quartet NGC 6845. The H i emission extends over all four galaxies but can only be associated clearly with the two spiral galaxies, NGC 6845A and B, which show signs of strong tidal interaction. We derive a total H i mass of at least 1.8 x 10(10) M-., most of which is associated with NGC 6845A, the largest galaxy of the group. We investigate the tidal interaction between NGC 6845A and B by studying the kinematics of distinct H i components and their relation to the known H ii regions. No H i emission is detected from the two lenticular galaxies, NGC 6845C and D. A previously uncatalogued dwarf galaxy, ATCA J2001-4659, was detected 4.4 arcmin NE from NGC 6845B and has an H i mass of similar to5 x 10(8) M-.. No H i bridge is visible between the group and its newly detected companion. Extended 20-cm radio continuum emission is detected in NGC 6845A and B as well as in the tidal bridge between the two galaxies. We derive star formation rates of 15-40 M-. yr(-1).
9 citations
TL;DR: In this article, the authors have mapped the large-scale distribution and kinematics of the atomic gas in the NGC 6872/IC 4970 system and carried out N-body simulations.
Abstract: The luminous barred galaxy NGC 6872 is one of the largest spiral galaxies known. Star formation is traced all along the arms, which extend over more than 100 kpc. The galaxy is likely to be affected by tidal perturbations from the nearby companion IC 4970 passing by on a low-inclination, prograde orbit. We have mapped the large-scale distribution and kinematics of the atomic gas in the NGC 6872/IC 4970 system and carried out N-body simulations. Our aim is to investigate the evolution of gas and stars in such close encounters, examine the influence of a dark matter halo on the length of the tidal tails, and test models of collisionally induced star formation.
7 citations