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Register a new userThe isolated interacting galaxy pair NGC 5426/27 (Arp 271)
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Added by
Isaura Fuentes-Carrera
Publication date
2003
fields
Physics
and research's language is
English
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We present H alpha observations of the isolated interacting galaxy pair NGC 5426/27 using the scanning Fabry-Perot interferometer PUMA. The velocity field, various kinematical parameters and rotation curve for each galaxy were derived. The FWHM map and the residual velocities map were also computed to study the role of non-circular motions of the gas. Most of these motions can be associated with the presence of spiral arms and structure such as central bars. We found a small bar-like structure in NGC 5426, a distorted velocity field for NGC 5427 and a bridge-like feature between both galaxies which seems to be associated with NGC 5426. Using the observed rotation curves, a range of possible masses was computed for each galaxy. These were compared with the orbital mass of the pair derived from the relative motion of the participants. The rotation curve of each galaxy was also used to fit different mass distribution models considering the most common theoretical dark halo models. An analysis of the interaction process is presented and a possible 3D scenario for this encounter is also suggested.
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In optical images, the not amply studied isolated interacting galaxy pair KPG 486 (NGC 6090) displays similar features to the galaxy pair The Antennae (NGC 4038/39). To compare the distribution of ionized hydrogen gas, morphology and kinematic and dynamic behaviour between both galaxy pairs, we present observations in the H$alpha$ emission line of NGC 6090 acquired with the scanning Fabry-Perot interferometer, PUMA. For each galaxy in NGC 6090 we obtained several kinematic parameters, its velocity field and its rotation curve, we also analysed some of the perturbations induced by their encounter. We verified the consistency of our results by comparing them with kinematic results from the literature. The comparison of our results on NGC 6090 with those obtained in a previous similar kinematic analysis made for The Antennae highlighted great differences between these galaxy pairs.
Encounters between galaxies modify their morphology, kinematics, and star formation (SF) history. The relation between these changes and external perturbations is not straightforward. The great number of parameters involved requires both the study of large samples and individual encounters where particular features, motions, and perturbations can be traced and analysed in detail. We analysed the morphology, kinematics, and dynamics of two luminous infrared spiral galaxies, NGC 5257 and NGC 5258, in which SF is mostly confined to the spiral arms, in order to understand interactions between galaxies of equivalent masses and SF processes during the encounter. Using scanning Fabry-Perot interferometry, we studied the contribution of circular and non-circular motions and the response of the ionized gas to external perturbations. We compared the kinematics with direct images of the pair and traced the SF processes and gravitational effects due to the presence of the other galaxy. The SED of each member of the pair was fitted. A mass model was fitted to the rotation curve of each galaxy. Large, non-circular motions detected in both galaxies are associated with a bar, spiral arms, and HII regions for the inner parts of the galaxies, and with the tidal interaction for the outer parts of the discs. Bifurcations in the rotation curves indicate that the galaxies have recently undergone their pericentric passage. The pattern speed of a perturbation of one of the galaxies is computed. Location of a possible corotation seems to indicate that the gravitational response of the ionized gas in the outer parts of the disc is related to the regions where ongoing SF is confined. The SED fit indicates a slightly different star formation history for each member of the pair. For both galaxies, a pseudo-isothermal halo better fits the global mass distribution.
Two 5 square degree regions around the NGC 7332/9 galaxy pair and the isolated galaxy NGC 1156 have been mapped in the 21-cm line of neutral hydrogen (HI) with the Arecibo L-band Feed Array out to a redshift of ~0.065$ (~20,000$ km/s) as part of the Arecibo Galaxy Environment Survey. One of the aims of this survey is to investigate the environment of galaxies by identifying dwarf companions and interaction remnants; both of these areas provide the potential for such discoveries. The neutral hydrogen observations were complemented by optical and radio follow-up observations with a number of telescopes. A total of 87 galaxies were found, of which 39 (45 per cent) were previously cataloged and 15 (17 per cent) have prior redshifts. Two dwarf galaxies have been discovered in the NGC 7332 group and a single dwarf galaxy in the vicinity NGC 1156 . A parallel optical search of the area revealed one further possible dwarf galaxy near NGC 7332.
We present results from our Giant Metrewave Radio Telescope (GMRT) HI, Himalayan Chandra Telescope (HCT) Halpha, 1m Sampurnanand Telescope (ST) and 1.3m Devasthal Fast Optical Telescope (DFOT) deep optical observations of NGC 7805/6 (Arp 112) system to test KUG 2359+311s tidal dwarf galaxy (TDG) candidacy and explore the properties of the interacting system. Our GMRT HI map shows no HI detection associated with KUG 2359+311, nor any HI tail or bridge-like structure connecting KUG 2359+311 to the NGC 7805/6 system. Our HCT Halpha image on the other hand, shows strong detections in KUG 2359+311, with net SFR ~ 0.035$pm 0.009 {rm M}_{odot},{rm yr}^{-1}$. The Halpha data constrains the redshift of KUG 2359+311 to $0.00 le z le 0.043$, compared to the redshift of NGC 7806 of ~ 0.015. TDGs detected to date have all been HI rich, and displayed HI, ionised gas and stellar tidal debris trails (bridges or tails) linking them to their parent systems. But neither our HI data nor our optical images, while three magnitudes deeper than SDSS, reveal tidal trail connecting KUG 2359+311 to NGC 7805/6. Lack of HI , presence of an old stellar population, ongoing star formation, reasonably high SFR compared to normal dwarf galaxies suggest that KUG 2359+311 may not be an Arp 112 TDG. It is most likely a case of a regular gas-rich dwarf galaxy undergoing a morphological transformation after having lost its entire gas content to an interaction with the Arp 112 system. Redshift and metallicity from future spectroscopic observations of KUG 2359+311 would help clarify the nature of this enigmatic structure.
We studied the apparent galaxy pair NGC 1232 / NGC 1232A with Chandra, looking for evidence of interactions and collisions. We report that there is no cloud of diffuse emission in NGC 1232, contrary to previous claims in the literature. Instead, we find that the small companion galaxy NGC 1232A contains three ultraluminous X-ray sources (ULXs) with peak 0.3-10 keV luminosities above 10^{40} erg/s (assuming a cosmological distance of 93 Mpc for this galaxy). For its mass, morphology, metal abundance and bright ULX population, NGC 1232A is analogous to the more nearby late-type spiral NGC 1313.
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