ESO 603-G21: A strange polar-ring galaxy

We present the results of B, V, R surface photometry of ESO603-G21 - a galaxy with a possible polar ring. The morphological and photometric features of this galaxy are discussed. The central round object of the galaxy is rather red and presents a nearly exponential surface brightness distribution. This central structure is surrounded by a blue warped ring or disk. The totality of the observed characteristics (optical and NIR colors, strong color gradients, HI and H_2 content, FIR luminosity and star-formation rate, rotation-curve shape, global mass-to-luminosity ratio, the agreement with the Tully-Fisher relation, etc.) shows that ESO603-G21 is similar to late-type spiral galaxies. We suppose that morphological peculiarities and the possible existence of two large-scale kinematically-decoupled subsystems in ESO603-G21 can be explained as being a result of dissipative merging of two spiral galaxies or as a consequence of a companion accretion onto a pre-existing spiral host.Comment: 8 pages, Astron. Astrophys, accepte

A first study of the galaxy HRG 2304 and its companion AM 1646-795 (NED01)

Aims. We report the first study of the peculiar ring-like galaxy HRG 2304 (NED02),which was previously classified as a ring galaxy with an elliptical smooth ring. This object was selected to prove that it is a candidate for the Solitaire-type ring galaxies in an early stage of ring formation. The main goal of this work is to provide the spectral characteristics of the current object and its companion AM 1646-795 (NED01). Methods. The study is based on spectroscopic observations in the optical band to highlight the characteristics of this interacting galaxy. To investigate the star formation history of HRG 2304 we used the stellar population synthesis code STARLIGHT. The direct V and B broad band images were used to enhance some fine structures. Results. Along the entire long-slit signal, the spectra of HRG 2304 and its companion resemble that of an early-type galaxy. We estimated a heliocentric systemic redshift of z = 0.0415, corresponding to heliocentric velocities of 12449 km s-1 for HRG 2304 (NED02) and 12430 km s-1 for AM1646-795 (NED01). The spatial variation in the contribution of the stellar population components for both objects are dominated by an old stellar population 2x10^9 < t < 13x10^9 yr. The observed radial-velocity distribution and the fine structures around HRG 2304 suggest an ongoing tidal interaction of both galaxies. Conclusions.The spectroscopic results and the morphological peculiarities of HRG 2304 can be adequately interpreted as an ongoing interaction with the companion galaxy. Both galaxies are early-type, the companion is elliptical, and the smooth distribution of the material around HRG 2304 and its off-center nucleus in the direction of AM1646-795 (NED01) characterize HRG 2304 as a Solitaire-type galaxy candidate in an early stage of ring formation.Comment: Accepted for publication in Astronomy and Astrophysics, 9 pages, 10 figures and 3 table

FM 047-02: a collisional pair of galaxies with a ring

Aims. We investigate the nature of the galaxy pair FM 047-02, which has been proposed as an archetype of the Solitaire types of peculiar (collisional) ring galaxies. Methods. The study is based on long-slit spectrophotometric data in the range of 3500-9500 angstrons obtained with the Gemini Multi-ObjectComment: 07 pages, 06 figures, 02 tables. arXiv admin note: text overlap with arXiv:1206.071

Galaxy transmutations: The double ringed galaxy ESO 474-G26

Surface photometry and a 21cm HI line spectrum of the giant double-ringed galaxy ESO 474-G26 are presented. The morphology of this system is unique among the 30,000 galaxies with >B15. Two almost orthogonal optical rings with diameters of 60 and 40 kpc surround the central body (assuming H0=70 km/s/Mpc). The outer one is an equatorial ring, while the inner ring lies in a nearly polar plane. The rings have blue optical colors typical of late-type spirals. Both appear to be rotating around the central galaxy, so that this system can be considered as a kinematically confirmed polar ring galaxy. Its observational characteristics are typical of galaxy merger remnants. Although the central object has a surface brightness distribution typical of elliptical galaxies, it has a higher surface brightness for its effective radius than ordinary ellipticals. Possible origins of this galaxy are discussed and numerical simulations are presented that illustrate the formation of the two rings in the merging process of two spiral galaxies, in which the observed appearance of ESO 474-G26 appears to be a transient stage.Comment: Accepted for publication in A&

AM 1934-563: A giant spiral polar-ring galaxy in a triplet

We have observed the emission-line kinematics and photometry of a southern triplet of galaxies. The triplet contains a giant spiral galaxy AM 1934-563 which optical structure resembles a polar-ring galaxy: distorted spiral disk, seen almost edge-on, and a faint large-scale (45 kpc in diameter) warped structure, inclined by 60^o-70^o with respect to the disk major axis. The triplet shows relatively small velocity dispersion (69 km/s) and a large crossing time (0.17 in units of the Hubble time). The disk of AM 1934-563 demonstrates optical colors typical for an early-type spirals, strong radial color gradient, and almost exponential surface brightness distribution with an exponential scale-length value of 3.1 kpc (R passband). The galaxy shows a maximum rotation velocity of about 200 km/s and it lies close to the Tully-Fisher relation for spiral galaxies. The suspected polar ring is faint (\mu(B) > 24) and strongly warped. Its total luminosity comprises (10-15)% of the total luminosity of AM 1934-563. We then try to model this system using numerical simulations, and study its possible formation mechanisms. We find that the most robust model, that reproduces the observed characteristics of the ring and the host galaxy, is the tidal transfer of mass from a massive gas-rich donor galaxy to the polar ring. The physical properties of the triplet of galaxies are in agreement with this scenario.Comment: Accepted for publication in A&

A study of the remarkable galaxy system AM 546-324 (the core of Abell S0546)

We report first results of an investigation of the tidally disturbed galaxy system AM\,546-324, whose two principal galaxies 2MFGC 04711 and AM\,0546-324 (NED02) were previously classified as interacting doubles. This system was selected to study the interaction of ellipticals in a moderately dense environment. We provide spectral characteristics of the system and present an observational study of the interaction effects on the morphology, kinematics, and stellar population of these galaxies. The study is based on long-slit spectrophotometric data in the range of $\sim$ 4500-8000 $\AA$ obtained with the Gemini Multi-Object Spetrograph at Gemini South (GMOS-S). We have used the stellar population synthesis code STARLIGHT to investigate the star formation history of these galaxies. The Gemini/GMOS-S direct r-G0303 broad band pointing image was used to enhance and study fine morphological structures. The main absorption lines in the spectra were used to determine the radial velocity. Along the whole long-slit signal, the spectra of the Shadowy galaxy (discovered by us), 2MFGC 04711, and AM\,0546-324 (NED02) resemble that of an early-type galaxy. We estimated redshifts of z= 0.0696, z= 0.0693 and z= 0.0718, corresponding to heliocentric velocities of 20\,141 km s$^{-1}$, 20\,057 km s$^{-1}$, and 20\,754 km s$^{-1}$ for the Shadowy galaxy, 2MFGC 04711 and AM\,0546-324 (NED02), respectively. ..

Nuclear spectra of polar-ring galaxies

We report the results of spectroscopic observations of 8 southern polar-ring galaxies (PRGs), in the wavelength range 5900-7300 \AA. We fing that 5 out of 8 galaxies contain LINERs or Sy nuclei. Taking into consideration all PRGs with available spectral data, we estimate that about half of all PRGs and PRG candidates have either LINER or Seyfert nuclei. The observed widths of the [NII]6583 line in the nuclei of early-type PRGs follow the linewidth - absolute luminosity relation for normal E/S0 galaxies. We found that one of the observed galaxies - ESO 576-G69 - is a new kinematically-confirmed polar-ring galaxy with a spiral host.Comment: 7 pages, 4 postscript figures, accepted for publication in MNRA

UGC 7388: a galaxy with two tidal loops

We present the results of spectroscopic and morphological studies of the galaxy UGC7388 with the 8.1-m Gemini North telescope. Judging by its observed characteristics, UGC7388 is a giant late-type spiral galaxy seen almost edge-on. The main body of the galaxy is surrounded by two faint (\mu(B) ~ 24 and \mu(B) ~ 25.5) extended (~20-30 kpc) loop-like structures. A large-scale rotation of the brighter loop about the main galaxy has been detected. We discuss the assumption that the tidal disruption of a relatively massive companion is observed in the case of UGC7388. A detailed study and modeling of the observed structure of this unique galaxy can give important information about the influence of the absorption of massive companions on the galactic disks and about the structure of the dark halo around UGC7388.Comment: 8 pages, 5 figure

The 3-D ionization structure of the planetary nebula NGC6565

A detailed study of the planetary nebula NGC6565 has been carried out on long-slit echellograms at six, equally spaced position angles. The expansion velocity field, the c(Hbeta) distribution and the radial profile of the physical conditions (electron temperature and density) are obtained. The distance, radius, mass and filling factor of the nebula and the temperature and luminosity of the central star are derived. The radial ionization structure is analyzed using both the classical method and the photo-ionization code CLOUDY. Moreover, we present the spatial structure in a series of images from different directions. NGC6565 is a young (2000--2500 years), patchy, optically thick triaxial ellipsoid projected almost pole-on. The matter close to major axis was swept-up by some accelerating agent forming two faint and asymmetric polar cups. A large cocoon of almost neutral gas completely embeds the ionized nebula. NGC6565 is in a recombination phase. The stellar decline started about 1000 years ago, but the main nebula remained optically thin for other 600 years before the recombination phase occurred. In the near future the ionization front will re-grow, since the dilution factor due to the expansion will prevail on the slower and slower stellar decline. NGC6565 is at a distance of 2.0(+-0.5) Kpc and can be divided into three radial zones: the ``fully ionized'' one, extending up to 0.029--0.035 pc at the equator (0.050 pc at the poles), the ``transition'' one, up to 0.048--0.054 pc (0.080 pc), the ``halo'', detectable up to 0.110 pc. The ionized mass (~0.03 Modot) is only a fraction of the total mass (> 0.15 Modot), which has been ejected by an equatorial enhanced superwind of 4(+-2)x10^(-5) Modot/yr lasted for 4(+-2)x10^3 years.Comment: 20 pages, 6 figures included + 10 JPEG figures, A&A accepted, postscript available at http://merlino.pd.astro.it/~supern/ps/ngc6565.p