Two-dimensional warm gas kinematics in interacting galaxy systems

Monthly Notices of the Royal Astronomical Society, Jan 2005

Gas reservoirs, internal or acquired, play an important role in the secular evolution of interacting galaxies, since they are able to enhance/trigger star formation episodes and, probably, feed the activity of active galactic nuclei. Using Fabry–Perot observations, we have mapped, in the Hα line, the warm (T≈ 104) gas distribution and the velocity fields of the galaxy members of five interacting, gas-rich galaxy systems. We investigated two M51-like systems (Arp 70 and Arp 74), two systems containing highly disrupted members (WBL 366 and RR 24) and a case of merging in progress (Arp 299, one of the nearest luminous infrared objects). We detected gas motions following the elongated arm/tail of Arp 70b, while in the fainter member of the pair of galaxies, Arp 70a, the gas distribution is off-centred with respect to the stellar isophotes, suggesting an external acquisition. Our kinematic data highlighted non-circular motions in the velocity field of one of the members of Arp 74 (Arp 74a). The two galaxies of the RR 24 system are connected by one tidal tail, through which the kinematically disturbed component RR 24b seems to supply warm gas to RR 24a. In spite of the nearly irregular gas distribution and perturbed morphology, WBL 366a (the star-forming galaxy VV-523) and WBL 366b have nearly regular velocity fields. The velocity field in the Arp 299 system is irregular, and gas flow between the two nuclei is detected. The present observations, discussed in the light of model predictions and complementary observations from the literature, suggest that all these systems are still probably in an early phase of the encounter. However, the ionized gas distribution and kinematics are strongly influenced by tidal forces. In particular, cross-fuelling mechanisms between galaxies are in action. In Arp 299 the warm and cold gaseous components show similar kinematic properties, although the cold gas seems to maintain a still better organized motion with respect to the warm gas.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://mnras.oxfordjournals.org/content/356/3/1177.full.pdf

Two-dimensional warm gas kinematics in interacting galaxy systems

R. Rampazzo 2 H. Plana 1 P. Amram 0 S. Bagarotto 2 J. Boulesteix 0 M. Rosado 3 0 Observatoire Astronomique de Marseille-Provence and Laboratoire d'Astrophysique de Marseille , 2 Place Le Verrier, 13248 Marseille Cedex 04, France 1 Department Ciencias Exatas e Tecnologicas, Universidade Estadual de Santa Cruz , Ilheus, BA, Brazil 2 Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy 3 Instituto de Astronomia , UNAM, Apartado Postal 70-264, Ciudad Universitaria , Mexico DF, CP 04510, Mexico A B S T R A C T Gas reservoirs, internal or acquired, play an important role in the secular evolution of interacting galaxies, since they are able to enhance/trigger star formation episodes and, probably, feed the activity of active galactic nuclei. Using Fabry-Perot observations, we have mapped, in the H line, the warm (T 104) gas distribution and the velocity fields of the galaxy members of five interacting, gas-rich galaxy systems. We investigated two M51-like systems (Arp 70 and Arp 74), two systems containing highly disrupted members (WBL 366 and RR 24) and a case of merging in progress (Arp 299, one of the nearest luminous infrared objects). We detected gas motions following the elongated arm/tail of Arp 70b, while in the fainter member of the pair of galaxies, Arp 70a, the gas distribution is off-centred with respect to the stellar isophotes, suggesting an external acquisition. Our kinematic data highlighted noncircular motions in the velocity field of one of the members of Arp 74 (Arp 74a). The two galaxies of the RR 24 system are connected by one tidal tail, through which the kinematically disturbed component RR 24b seems to supply warm gas to RR 24a. In spite of the nearly irregular gas distribution and perturbed morphology, WBL 366a (the star-forming galaxy VV523) and WBL 366b have nearly regular velocity fields. The velocity field in the Arp 299 system is irregular, and gas flow between the two nuclei is detected. The present observations, discussed in the light of model predictions and complementary observations from the literature, suggest that all these systems are still probably in an early phase of the encounter. However, the ionized gas distribution and kinematics are strongly influenced by tidal forces. In particular, cross-fuelling mechanisms between galaxies are in action. In Arp 299 the warm and cold gaseous components show similar kinematic properties, although the cold gas seems to maintain a still better organized motion with respect to the warm gas. - (Sulentic 1989; Xu & Sulentic 1991; Hernandez-Toledo & Puerari 1999; Hernandez-Toledo, Dultzin-Hacyan & Sulentic 2001) show unambiguous evidence for interaction-induced star formation in the spiral components of the pairs. Further, recent ISO and H observations of 17 mixed E + S pairs indicate that some of the early-type components are cross-fuelled by their spiral companions (Domingue et al. 2003). In the secular evolution of galaxies, the gas reservoir then acquires a fundamental importance since it regulates star formation episodes and, probably, feeds the activity of active galactic nuclei (AGN). Schematically, models of galaxy encounters predict that a galaxy galaxy interaction influences gas behaviour in two ways. First, a perturber exerts its gravitational force directly upon the gas in the form of a tidal force and makes the gas deviate from its original motion. Secondly, a perturber also deforms the distribution of stars in the parent galaxy by tidal forces, and the resulting deformation of the gravitational potential may affect the gas motion. The bar, probably created in the stellar disc as a direct consequence of the tidal force exerted by a perturber, has gained ground as one of the mechanisms able to induce gas flows towards the galaxy centre (see e.g. Noguchi 1988; Gerin, Combes & Athanassoula 1990; Salo 1991; Miwa & Noguchi 1998; Berentzen et al. 2004) since the first phases of an encounter. Mechanisms like cross-fuelling via small accretions may also be in action (see e.g. Salo & Laurikainen 1993) to feed gas to the galaxy centre. Small accretions of matter should mark the history of galaxies, and not only modify their photometric properties. Indeed, the observed kinematic phenomena retain a memory of the accretion processes driving their formation/evolution. Stellar and gas components with a misaligned or even opposite angular momentum with respect to the host galaxy are often found, not only in early-type galaxies but, recently, also in gas-rich morphological types, like spirals (see e.g. Corsini & Bertola 1998; Bertola et al. 1999; Sarzi et al. 2000; Corsini, Pizzella & Bertola 2002). The statistics of the occurrence of these phenomena is still very poor since they are discovered only by measuring detailed gas and stellar kinematics. We lack an overall picture of the effective weight played by secondary events in shaping Hubble types. Our understanding of the kinematic behaviour of the dif (...truncated)


This is a preview of a remote PDF: https://mnras.oxfordjournals.org/content/356/3/1177.full.pdf

R. Rampazzo, H. Plana, P. Amram, S. Bagarotto, J. Boulesteix, M. Rosado. Two-dimensional warm gas kinematics in interacting galaxy systems, Monthly Notices of the Royal Astronomical Society, 2005, pp. 1177-1190, 356/3, DOI: 10.1111/j.1365-2966.2004.08549.x