The nuclear ring in the unbarred galaxy NGC 278: Result of a minor merger?

Knapen, Johan H.; Whyte, L.; Blok, de Erwin; Hulst, van der Thijs

doi:10.1051/0004-6361:20034336

Cited by 51 publications

(69 citation statements)

References 34 publications

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“…HI its diameter is five times greater (Knapen et al 2004). Its dust-rich central parts are quite bright not only in the Hα line, but also in the infrared continuum (Dale et al 2000;Sanders et al 2003) and the [CII] line (Malhotra et al 2001) consistent with intense star-forming activity (Ho et al 1995;Eskridge et al 2002).…”

Section: Ngc 278 = Ddomentioning

confidence: 94%

CI and CO in nearby galaxy centers

Israel¹

2009

A&A

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Aims. We study the physical properties and mass of molecular gas in the central regions of galaxies with active nuclei. Methods. Maps and measurements of the J = 1-0, J = 2-1, J = 3-2, J = 4-3 12 CO, the J = 1-0, J = 2-1 and J = 3-2 13 CO lines in the central arcminute squared of NGC 278, NGC 660, NGC 3628, NGC 4631, and NGC 4666, as well as 492 GHz [CI] maps in three of these are used to model the molecular gas. Results. All five objects contain bright CO emission in the central regions. Clear central concentrations were found in NGC 660, NGC 3628, and NGC 4666, but not in the weakest CO emitters NGC 278 and NGC 4631. In all cases, the observed lines could be modeled only with at least two distinct gas components. The physical condition of the molecular gas is found to differ from galaxy to galaxy. Relatively tenuous (density 100-1000 cm −3 ) and high kinetic temperature (100-150 K) gas occur in all galaxies, except perhaps NGC 3628, mixed with cooler (10-30 K) and denser (0.3−1.0 × 10 4 cm −3 ) gas. The CO-to-H 2 conversion factor X is typically an order of magnitude less than the "standard" value in the Solar Neighborhood in all galaxy centers. The molecular gas is constrained within radii between 0.6 and 1.5 kpc from the nuclei. Within these radii, H 2 masses are typically 0.6−1.5 × 10 8 M , which corresponds to no more than a few per cent of the dynamical mass in the same region.

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Section: Ngc 278 = Ddomentioning

confidence: 94%

CI and CO in nearby galaxy centers

Israel¹

2009

A&A

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“…But galaxies with molecular rings have been found that have no bars (e.g. 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.…”

Section: "Wildfire" Vs Dynamicsmentioning

confidence: 99%

“…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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“…The non-barred nature of its host, NGC 7742, and the counterrotation observed in the central region might indicate that some past interactive event is responsible. For the similar non-barred nuclear ring host galaxy NGC 278, a past minor merger is indeed what we proposed as origin for its ring on the basis of the severely disturbed morphology and kinematics of its atomic gas (Knapen et al 2004). NGC 7742 has a companion galaxy, NGC 7743, but that seems too far away and of too regular morphology to be a candidate for a recent interaction.…”

Section: Physical Conditions Of the Gas: The Case Of Ngc 7742mentioning

confidence: 57%

Star Formation in the Central Regions of Galaxies

Knapen

Allard

Mazzuca

et al. 2008

Mapping the Galaxy and Nearby Galaxies

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Summary. Massive star formation in the central regions of spiral galaxies plays an important role in the dynamical and secular evolution of their hosts. Here, we summarise a number of recent investigations of the star formation history and the physical conditions of the gas in circumnuclear regions, to illustrate not only the detailed results one can achieve, but also the potential of using state-of-the-art spectroscopic and analysis techniques in researching the central regions of galaxies in general. We review how the star formation history of nuclear rings confirms that they are long-lived and stable configurations. Gas flows in from the disk, through the bar, and into the ring, where successive episodes of massive star formation occur. Analysing the ring in NGC 7742 in particular, we determine the physical conditions of the line emitting gas using a combination of ionisation and stellar population modelling, concluding that the origin of the nuclear ring in this non-barred galaxy lies in a recent minor merger with a small gas-rich galaxy.

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The nuclear ring in the unbarred galaxy NGC 278: Result of a minor merger?

Cited by 51 publications

References 34 publications

CI and CO in nearby galaxy centers

CI and CO in nearby galaxy centers

The NGC 1614 interacting galaxy

Star Formation in the Central Regions of Galaxies

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