NGC 7217: A Spheroid-dominated, Early-Type Resonance Ring Spiral Galaxy

Buta, Ronald J.; Driel, W.D. van; Braine, J.; Combes, F.; Wakamatsu, K.; Sofue, Yoshiaki; Tomita, Akihiko

doi:10.1086/176169

Cited by 47 publications

(57 citation statements)

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“…As is the case for NGC 3626, the central region of NGC 4772 is HI-poor. Furthermore, the deep optical photometry of the galaxy reveals the presence of a round, low surface brightness disk in the outer part, reminiscent of a similar feature reported by Buta et al (1995) in the Sab counterrotator NGC 7217.…”

Section: Ngc 4772supporting

confidence: 71%

The gas content of peculiar galaxies: Counterrotators and polar rings

Bettoni

Galletta

García‐Burillo

et al. 2001

A&A

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Abstract. This paper studies the global ISM content in a sample of 104 accreting galaxies, including counterrotators and polar rings, which spans the entire Hubble sequence. The molecular, atomic and hot gas content of accretors is compared to a newly compiled sample of normal galaxies. We present results of a small survey of the J = 1−0 line of 12 CO with the 15 m SEST telescope on a sample of 11 accretors (10 counterrotators and 1 polar ring). The SEST sample is enlarged with published data from 48 galaxies, for which observational evidence of counterrotation in the gas and/or the stars has been found. Furthermore, the available data on a sample of 46 polar ring galaxies has been compiled. In order to explore the existence of an evolutionary path linking the two families of accretors, the gas content of counterrotators and polar rings is compared. It was found that the normalized content of cold gas (Mgas/LB) in polar rings is ∼1 order of magnitude higher than the reference value derived for normal galaxies. The inferred gas masses are sufficient to stabilize polar rings through self-gravity. In contrast, it was found that the cold gas content of counterrotators is close to normal for all galaxy types. Although counterrotators and polar rings probably share a common origin, the gas masses estimated here confirm that light gas rings accreted by future counterrotators may have evolved faster than the self-gravitating structures of polar rings. In this scenario, the transformation of atomic into molecular gas could be enhanced near the transition region between the prograde and the retrograde disks, especially in late-type accretors characterized by a high content of primordial gas. This is tentatively confirmed in this work: the measured H2/HI ratio seems larger in counterrotators than in normal or polar ring galaxies for types later than S0s.

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Section: Ngc 4772supporting

confidence: 71%

The gas content of peculiar galaxies: Counterrotators and polar rings

Bettoni

Galletta

García‐Burillo

et al. 2001

A&A

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“…NGC 278 & NGC 7217, Knapen et al 2004;Sarzi et al 2007). It has been shown that other physical properties, e.g., a weak oval distortion (Buta et al 1995), a dissolved bar (Verdes-Montenegro et al 1995), tidal effects of a companion galaxy (Combes 1988a), or a recent minor merger (Knapen et al 2004;Mazzuca et al 2006) can cause the same effect as a bar: the non-axisymmetric potential caused by the bar can channel gas to the nucleus, which is slowed down near or at the inner Lindblad resonance. Elmegreen (1994) proposed a scenario in which the gravitational collapse of gas that is caught in an inner Lindblad resonance within a starburst ring, fueled by galactic bars or strong spiral arms, can lead to the formation of giant clouds with spots of intense star formation.…”

Section: "Wildfire" Vs Dynamicsmentioning

confidence: 99%

The NGC 1614 interacting galaxy

König

Aalto

Müller

et al. 2013

A&A

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Minor mergers frequently occur between giant and gas-rich low-mass galaxies and can provide significant amounts of interstellar matter to refuel star formation and power active galactic nuclei (AGN) in the giant systems. Major starbursts and/or AGN result when fresh gas is transported and compressed in the central regions of the giant galaxy. This is the situation in the starburst minor merger NGC 1614, whose molecular medium we explore at half-arcsecond angular resolution through our observations of 12 CO (2−1) emission using the Submillimeter Array (SMA). We compare our 12 CO (2−1) maps with optical and Paα, Hubble Space Telescope and high angular resolution radio continuum images to study the relationships between dense molecular gas and the NGC 1614 starburst region. The most intense 12 CO emission occurs in a partial ring with ∼230 pc radius around the center of NGC 1614, with an extension to the northwest into the dust lane that contains diffuse molecular gas. We resolve ten giant molecular associations (GMAs) in the ring, which has an integrated molecular mass of ∼8 × 10 8 M . Our interferometric observations filter out a large part of the 12 CO (1−0) emission mapped at shorter spacings, indicating that most of the molecular gas is diffuse and that GMAs only exist near and within the circumnuclear ring. The molecular ring is uneven with most of the mass on the western side, which also contains GMAs extending into a pronounced tidal dust lane. The spatial and kinematic patterns in our data suggest that the northwest extension of the ring is a cosmic umbilical cord that is feeding molecular gas associated with the dust lane and tidal debris into the nuclear ring, which contains the bulk of the starburst activity. The astrophysical process for producing a ring structure for the final resting place of accreted gas in NGC 1614 is not fully understood, but the presence of numerous GMAs suggests an orbit-crowding or resonance phenomenon. There is some evidence that star formation is progressing radially outward within the ring, indicating that a self-triggering mechanism may also affect star formation processes. The net result of this merger therefore very likely increases the central concentration of stellar mass in the NGC 1614 remnant giant system.

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“…Sarzi et al discuss how the formation of such rings may, instead of being caused by strong bars, originate due to a weak oval distortion or the tidal effects of a companion (e.g. Combes 1988b; Buta et al 1995). Knapen et al (2004) find a nuclear ring in NGC 278 triggered by the non-axisymmetric potential induced by a recent minor merger.…”

Section: Is There a Bar In Ngc 1614?mentioning

confidence: 99%

Star-formation in the central kpc of the starburst/LINER galaxy NGC 1614

Olsson

Aalto

Thomasson

et al. 2010

A&A

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Aims. The aim is to investigate the star-formation and LINER (low ionization nuclear emission line region) activity within the central kiloparsec of the galaxy NGC 1614. In this paper the radio continuum morphology, which provides a tracer of both nuclear and star-formation activity, and the distribution and dynamics of the cold molecular and atomic gas feeding this activity, are studied. In particular, the nature of an R ≈ 300 pc nuclear ring of star-formation and its relationship to the LINER activity in NGC 1614 is addressed. Methods. A high angular resolution, multi-wavelength study of the LINER galaxy NGC 1614 has been performed. Deep observations of the CO 1-0 spectral line were performed using the Owens Valley Radio Observatory (OVRO). These data have been complemented by extensive multi-frequency radio continuum and Hi absorption observations using the Very Large Array (VLA) and Multi-Element Radio Linked Interferometer Network (MERLIN). Results. Toward the center of NGC 1614, we have detected a ring of radio continuum emission with a radius of 300 pc. This ring is coincident with previous radio and Paα observations. The dynamical mass of the ring based on Hi absorption is 3.1 × 10 9 M . The peak of the integrated CO 1-0 emission is shifted by 1 to the north-west of the ring center. An upper limit to the molecular gas mass in the ring region is ∼1.7 × 10 9 M . Inside the ring, there is a north to south elongated 1.4 GHz radio continuum feature, with a nuclear peak. This peak is also seen in the 5 GHz radio continuum and in the CO. Conclusions. We suggest that the R = 300 pc star forming ring represents the radius of a dynamical resonance -as an alternative to the scenario that the starburst is propagating outwards from the center into a molecular ring. The ring-like appearance is probably part of a spiral structure. Substantial amounts of molecular gas have passed the radius of the ring and reached the nuclear region. The nuclear peak seen in 5 GHz radio continuum and CO is likely related to previous star formation, where all molecular gas was not consumed. The LINER-like optical spectrum observed in NGC 1614 may be due to nuclear starburst activity, and not to an active galactic nucleus (AGN). Although the presence of an AGN cannot be excluded.

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NGC 7217: A Spheroid-dominated, Early-Type Resonance Ring Spiral Galaxy

Cited by 47 publications

References 0 publications

The gas content of peculiar galaxies: Counterrotators and polar rings

The gas content of peculiar galaxies: Counterrotators and polar rings

The NGC 1614 interacting galaxy

Star-formation in the central kpc of the starburst/LINER galaxy NGC 1614

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