Detection of CO emission in Hydra 1 cluster galaxies

A survey of bright Hydra cluster spiral galaxies for the CO(1-0) transition at 115 GHz was performed with the 15m Swedish-ESO submillimeter telescope (SEST). Five out of 15 galaxies observed have been detected in the CO(1-0) line. The largest spiral galaxy in the cluster, NGC 3312, got more CO than any spiral of the Virgo cluster. This Sa-type galaxy is optically largely distorted and disrupted on one side. It is a good candidate for ram pressure stripping while passing through the cluster's central region. A comparison with global CO properties of Virgo cluster spirals shows a relatively good agreement with the detected Hydra cluster galaxies

Molecular gas content of galaxies in the Hydra-Centaurus supercluster

A survey of bright spiral galaxies in the Hydra-Centaurus supercluster for the CO(1-0) transition at 115 GHz was performed with the 15m Swedish-ESO submillimeter telescope (SEST). A total of 30 galaxies have been detected in the CO(1-0) transition out of 47 observed, which is a detection rate over 60%. Global physical parameters of these galaxies derived from optical, CO, HI, and IR measurements compare very well with properties of galaxies in the Virgo cluster

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 the Karachentsev catalog of previously unknown nearby dwarf galaxies (Karachentseva & Karachentsev 1998). This survey covers all known nearby galaxy groups within the Local Volume (i.e. within 10 Mpc) and their environment, that is about 25% of the total sky. A total of 257 galaxies have been observed with a detection rate of 60%. We searched a frequency band corresponding to heliocentric radial velocities from -470 km/s to about +4000 km/s. Non-detections are either due to limited coverage in radial velocity, confusion with Local HI (mainly in the velocity range -140 km/s to +20 km/s, or lack of sensitivity for very weak emission. 25% of the detected galaxies are located within the Local Volume. Those galaxies are dwarf galaxies judged by their optical linear diameter (1.4 +/- 0.2 kpc on the average), their mean total HI mass (4.6 E7 solar masses), and their observed linewidths (39 km/s).Comment: 22 pages, 9 ps figures, A&AS, in pres

HI properties of nearby galaxies from a volume-limited sample

We consider global HI and optical properties of about three hundred nearby galaxies with V$_0 < 500$ km/s. The majority of them have individual photometric distance estimates. The galaxy sample parameters, e.g. their linear diameters, their HI mass-to-luminosity ratio, their total mass-to-luminosity ratio, their mean optical surface brightness show some known and some new correlations implying a meaningful dynamic explanation. For the LV galaxies their HI mass and angular momentum follow a nearly linear relation expected for rotating gaseous disks being near the threashold of gravitational instability, favourable for active star formation.Comment: 5 pages, 9 figures, uses laa.sty accepted by A&A Suppl. Serie

HI studies of the Sculptor group galaxies. VIII. The background galaxies: NGC 24 and NGC 45

In order to complete our HI survey of galaxies in the Sculptor group area, VLA observations of NGC 24 and NGC 45 are presented. These two galaxies of similar magnitude M_B ~ -17.4 lie in the background of the Sculptor group and are low surface brightness galaxies, especially NGC 45. The HI distribution and kinematics are regular for NGC 24 while NGC 45 exhibits a kinematical twist of its major axis. A tilted-ring model shows that the position angle of the major axis changes by ~25 degrees. A best-fit model of their mass distribution gives mass-to-light ratios for the stellar disk of 2.5 and 5.2 for NGC 24 and NGC 45 respectively. These values are higher than the ones expected from stellar population synthesis models. Despite the large dark matter contribution, the galaxy mass is still dominated by the stellar component in their very inner regions. These high mass-to-light ratios are typical of what is seen in low surface brightness galaxies and may indicate that, in those galaxies, disks are far from the maximum disk case. The halo parameters derived from the best-fit models are thus lower limits.Comment: 23 pages, 10 figures, accepted for publication in The Astronomical Journa

Tidally Compressed Gas in Centers of Early Type and Ultraluminous Galaxies

In this paper we propose that the compressive tidal field in the centers of flat-core early type galaxies and ultraluminous galaxies compresses molecular clouds producing dense gas obseved in the centers of these galaxies. The effect of galactic tidal fields is usually considered disruptive in the literature. However, for some galaxies, the mass profile flattens towards the center and the resulting galactic tidal field is not disruptive but instead it is compressive within the flat-core region. We have used the virial theorem to determine the minimum density of a molecular cloud to be stable and gravitationally bound within the tidally compressive region of a galaxy. We have applied the mechanism to determine the mean molecular cloud densities in the centers of a sample of flat-core, early-type galaxies and ultraluminous galaxies.Comment: 18 latex pages and uses aaspp4.sty, accepted for publication in Astrophysical Journa

The extent of NGC 6822 revealed by its C stars population

Using the CFH12K camera, we apply the four band photometric technique to identify 904 carbon stars in an area 28' x 42' centered on NGC 6822. A few C stars, outside of this area were also discovered with the Las Campanas Swope Telescope. The NGC 6822 C star population has an average I of 19.26 mag leading to an average absolute I magnitude of -4.70 mag, a value essentially identical to the mean magnitude obtained for the C stars in IC 1613. Contrary to stars highlighting the optical image of NGC 6822, C stars are seen at large radial distances and trace a huge slightly elliptical halo which do not coincide with the huge HI cloud surrounding NGC6822. The previously unknown stellar component of NGC 6822 has a exponential scale length of 3.0' +/- 0.1' and can be traced to five scale lengths. The C/M ratio of NGC 6822 is evaluated to br 1.0 +/- 0.2.Comment: accepted, to be published in A

The HI supershell GS061+00+51 and its neighbours

We describe HI observations of a 4 x 4 degrees field in the Milky Way centered on l=61 deg, b=0 deg made by the Effelsberg radiotelescope. The field contains one previously identified HI supershell, GS061+00+51 (Heiles, 1979); apart from it we find several new structures. We also study the HI distribution in the vicinity of four HII regions, S86, S87, S88 and S89. We confirm the existence of the shell GS061+00+51, and we find that it has two smaller neighbours, spherical shells with a radius around 30 pc. We identify at least one more regular shell at v_LSR = -18 km/s; and one blown-out shell at v_LSR = -54 km/s. In two cases we are able to connect HII regions with features in the HI distribution (S86 and S87), in two other cases no connection is found. Apart from quite regular HI shells we see a number of non-coherent objects, which are probably a result of the turbulence in the interstellar medium