We present a multiwavelength study of the highly evolved compact galaxy group known as Seyfert's Sextet (HCG79: SS). We interpret SS as a 2-3 Gyr more evolved analog of Stephan's Quintet (HCG92: SQ). ...We postulate that SS formed by sequential acquisition of 4-5 primarily late-type field galaxies. Four of the five galaxies show an early-type morphology which is likely the result of secular evolution driven by gas stripping. Stellar stripping has produced a massive/luminous halo and embedded galaxies that are overluminous for their size. These are interpreted as remnant bulges of the accreted spirals. H79d could be interpreted as the most recent intruder, being the only galaxy with an intact interstellar medium (ISM) and uncertain evidence for tidal perturbation. In addition to stripping activity we find evidence for past accretion events. H79b (NGC6027) shows a strong counter-rotating emission line component interpreted as an accreted dwarf spiral. H79a shows evidence for an infalling component of gas representing feedback or possible cross-fueling by H79d. The biggest challenge to this scenario involves the low gas fraction in the group. If SS formed from normal field spirals then much of the gas is missing. Finally, despite its advanced stage of evolution, we find no evidence for major mergers and infer that SS (and SQ) are telling us that such groups coalesce via slow dissolution.
We present Hα 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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Thousands of new asteroids are discovered every year and the rate of discovery is by far larger than the determination rate of their physical properties. In 2015 a group of researchers and students ...of several Mexican institutions have established an observational program to study asteroids photometrically. The program, named Mexican Asteroid Photometry Campaign, is aiming to derive rotation periods of asteroids based on optical photometric observations. Since then four campaigns have been carried out. The results obtained throughout these campaigns, as well as future work, are presented.
Context. Rotation curves of interacting galaxies often show that velocities are either rising or falling in the direction of the companion galaxy. Aims. We seek to reproduce and analyse these ...features in the rotation curves of simulated equal-mass galaxies suffering a one-to-one encounter as possible indicators of close encounters. Methods. Using simulations of major mergers in 3D, we study the time evolution of these asymmetries in a pair of galaxies during the first passage. Results. Our main results are: (a) the rotation curve asymmetries appear right at pericentre of the first passage, (b) the significant disturbed rotation velocities occur within a small time interval, of ${\sim}0.5~{\rm Gyr}\,h^{-1}$, and, therefore, the presence of bifurcation in the velocity curve could be used as an indicator of the pericentre occurrence. These results are in qualitative agreement with previous findings for minor mergers and flybys.
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Context. At intermediate redshifts, many galaxies seem to have experienced an interaction. It is not always straightforward to determine what type of encounter or perturbation is observed, nor the ...outcome of this event. In some cases, only the use of both morphological and kinematical information can determine the true configuration of an encounter at intermediate redshift. Aims. We present the morphological and kinematical analysis of a system at z = 0.74 to understand its configuration, interacting stage, and evolution. Methods. Using the integral field spectrograph GIRAFFE, long-slit spectroscopy by FORS2, direct optical images from the HST-ACS, and ISAAC near-infrared images, we determine the morphology of this system, its star-formation history, and its extended kinematics to propose a possible configuration for the system. Numerical simulations are used to test different interacting scenarii. Results. We identify this system to be a face-on disk galaxy with a very bright bar that is interacting with a smaller companion such that the galaxy and the companion have a mass ratio of 3:1. The relevance of kinematical information and the constraints that it imposes on the interpretation of the observations of distant galaxies are particularly greater in this case. Conclusions. This object represents one of the clearest examples of how one can misinterpret morphology in the absence of kinematical information.
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Aims.We study the kinematics and dynamics of the M 51-type interacting galaxy pair KPG 302 (NGC 3893/96). We analyze the perturbations induced by the encounter on each member of the pair, as well as ...the distribution of the dark matter (DM) halo of the main galaxy in order to explore possible differences between DM halos of “isolated” galaxies and those of galaxies belonging to a pair. Methods.The velocity field of each galaxy was obtained using scanning Fabry-Perot interferometry. A two-dimensional kinematic and dynamical analysis of each galaxy and the pair as a whole are done emphasizing the contribution of circular and non-circular velocities. Non-circular motions can be traced on the rotation curves of each galaxy allowing us to differentiate between motions associated to particular features and motions that reflect the global mass distribution of the galaxy. For the main galaxy of the pair, NGC 3893, optical kinematic information is complemented with HI observations from the literature to build a multi-wavelength rotation curve. We try to fit this curve with a mass-distribution model using different DM halos. Results.Non-circular motions are detected on the velocity fields of both galaxies. These motions can be associated to perturbations due to the encounter and, in the case of the main galaxy, to the presence of a structure such as spiral arms. The location of the corotation radius of this galaxy is also explored. We find that the multi-wavelength rotation curve of NGC 3893, “cleaned” from the effect of non-circular motions, cannot be fitted whether by a pseudo-isothermal or by a NFW DM halo.
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We present a kinematical study of the marginally edge-on galaxy ESO 379-006. With Fabry-Perot spectroscopy at Hα we obtain velocity maps, the radial velocity field, and position-velocity diagrams ...parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the galaxy and discuss the role of projection effects. The twisting of isovelocities in the radial velocity field of the disk of ESO 379-006 as well as a kinematical asymmetry found in the position-velocity diagrams parallel to the minor axis suggest the existence of non-circular motions that can be modeled by including a radial inflow besides the rotation motion. Extraplanar Diffuse Ionized gas was detected in this galaxy both from the images and from its kinematics. It is possible that the diffuse gas is lagging in rotation.
KPG 390: A pair of trailing spirals Repetto, P.; Rosado, M.; Gabbasov, R. ...
Proceedings of the International Astronomical Union,
06/2010, Volume:
6, Issue:
S271
Journal Article
Peer reviewed
Open access
In this study we present scanning Fabry-Perot Hα observations of the isolated interacting galaxy pair NGC 5278/79. We derived velocity fields, various kinematic parameters and rotation curves for ...both galaxies. These kinematical results together with the fact that dust lanes have been detected in both galaxies, as well as the analysis of surface brightness profiles along the minor axis, allowed us to determine univocally that both components of the interacting pair are trailing spirals. We have also estimated the mass of NGC 5278 fitting its rotation curve with a disk-halo component. We have tested three different types of halo (pseudo-isothermal, Hernquist and Navarro Frenk White) and we have obtained that the rotation curve can be fitted either with a pseudo-isothermal, an Hernquist halo or a Navarro Frenk White halo component, although in the first case the amount of dark matter required is about ten times smaller than for the other two halo distributions.
IMAGES Neichel, B.; Hammer, F.; Puech, M. ...
Astronomy and astrophysics (Berlin),
06/2008, Volume:
484, Issue:
1
Journal Article
Peer reviewed
We present a first combined analysis of the morphological and dynamical properties for the intermediate-mass Galaxy Evolution Sequence (IMAGES) sample. It is a representative sample of 52 z˜0.6 ...galaxies with M_stell from 1.5 to 15 × 1010~M that possesses 3D resolved kinematics and HST deep imaging in at least two broad band filters. We aim at evaluating the evolution of rotating spirals robustly since z˜ 0.6, as well as at testing the different schemes for classifying galaxies morphologically. We used all the information provided by multi-band images, color maps, and 2D light fitting to assign a morphological class to each object. We divided our sample into spiral disks, peculiar objects, compact objects, and mergers. Using our morphological classification scheme, 4/5 of the identified spirals are rotating disks, and more than 4/5 of identified peculiar galaxies show complex kinematics, while automatic classification methods such as concentration-asymmetry and GINI-M20 severely overestimate the fraction of relaxed disk galaxies. Using this methodology, we find that the fraction of undisturbed rotating spirals has increased by a factor ~2 during the past 6 Gyr, a much higher fraction than was found previously based on morphologies alone. These rotating spiral disks are forming stars very rapidly, even doubling their stellar masses over the past 6 Gyr, while most of their stars were formed a few Gyr earlier, which reveals a large gas supply. Because they are the likely progenitors of local spirals, we can conjecture how their properties are evolving. Their disks show some evidence of inside-out growth, and the gas supply/accretion is not random since the disk needs to be stable in order to match the local disk properties.
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