NGC 7421: Surfing the Intracluster Medium?

Ryder, S. D.; Purcell, Guy B.; Davis, David; Andersen, V.

doi:10.1071/as97081

Cited by 21 publications

(22 citation statements)

References 8 publications

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“…These authors suggest the action of the ram pressure as the reason for this shape. Even earlier the same suggestion was proposed by Ryder (1997) to explain the similar shape of HI halo of NGC 7421 galaxy and it is surely true for NGC 2276 galaxy as well (Fig. 3).…”

Section: Ram Pressure and Star Formationsupporting

confidence: 78%

On the origin of circular and hexagonal formations in galaxies

Efremov¹

2003

Astronomical & Astrophysical Transactions

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The round and arc-shaped formations are known in some galaxies, the Bubble complex (the Hodge object) in NGC 6946 being the most remarkable. The rim of the complex has a form of a regular arc in which a part of a hexagonal structure is embedded. A similar morphology is recognized in NGC 7421 galaxy, in that part of its rim which is leading in the galaxy motion through the intergalactic gas, as suggested by the bowshock appearance of the HI halo of the galaxy. A hexagonal shape is also found in NGC4676A galaxy. The HII radial velocities across the Bubble complex are compatible with its retrograde rotation and drift, which are characteristic for solitary vortices known in nonlinear hydrodynamics.The drift motion may explain the location of the Bubble complex at the tip of the largest elliptical HI hole in NGC 6946. The hexagonal vortices in the atmospheres of Jupiter and Saturn are within the gas streams what seems to be suggestive as well. It is conjectured that the hexagonal rims of stellar systems might be relicts of flat segments of the shock 1 wave produced by the ram pressure. The giant stellar arcs in NGC 300 and M33 are associated with the energetic X-ray sources P42 and X-4 respectively (fig. 11), and these might be the relics of Hypernovae.

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Section: Ram Pressure and Star Formationsupporting

confidence: 78%

On the origin of circular and hexagonal formations in galaxies

Efremov¹

2003

Astronomical & Astrophysical Transactions

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“…The modest compression of the H i contours on the eastern side of the galaxy relative to those on the western side suggests that the galaxy may be encountering a dense intergalactic medium. Unambiguous examples in which the H i distribution of a galaxy is being perturbed by the intergalactic medium are rare; the best are probably NGC 7421, a southern spiral with an arclike distribution of gas (Ryder et al 1997), and NGC 4522 (Kenney & Koopmann 1999). The H i morphology of IC 3476 is qualitatively similar to what is seen in NGC 7421 and NGC 4522, though it remains to be seen whether IC 3476 belongs to this class of object.…”

Section: Ic 3476mentioning

confidence: 50%

HiObservations of Barred Magellanic Spirals. II. The Frequency and Impact of Companions

Wilcots¹,

Prescott²

2004

Astron J

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The results of an H i 21 cm line survey of a sample of Magellanic spiral galaxies with apparent optical companions reveal that only four of 13 systems have confirmed H i-detected neighbors. The current interactions are affecting the morphology of the main galaxy in only two cases, NGC 3664 and NGC 3995. The presence of companions near NGC 2537 and UGC 5391 appears to have no effect on the morphology of those galaxies. Overall, there is little difference between the asymmetry of the H i profiles of those galaxies with and without companions, and on average, these Magellanic spirals have H i profiles that are no more asymmetric than a random sample of spirals in the field. We conclude that current interactions cannot be responsible for the lopsided morphology of most of the galaxies in this sample and that, whatever its original cause, lopsidedness must be a long-lived characteristic of these galaxies.

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“…The NGC 2442 system shares many of the characteristics of certain asymmetric galaxies that are suspected of being ram-pressure stripped of some of their H I as they pass through the intracluster medium. Among the best examples of this phenomenon are NGC 2276 (Gruendl et al 1993), NGC 4273 (Davis et al 1995), NGC 7421 (Ryder et al 1997), and the Virgo Cluster galaxies NGC 4388 (Veilleux et al 1999), NGC 4654 (Phookun & Mundy 1995), and NGC 4522 (Vollmer et al 2000). The most distinctive features of these objects are (1) strongly asymmetric H I pro-Ðles ; (2) a truncated optical and/or gas distribution on one side of the galaxy, often having a bow shockÈlike morphology ; (3) a gaseous tail or "" wake ÏÏ in the opposite direction, possibly out of the disk plane ; and (4) mild disturbance to an otherwise regular rotational velocity pattern.…”

Section: T Idal Encounter ?mentioning

confidence: 99%

HIPASS Detection of an Intergalactic Gas Cloud in the NGC 2442 Group

Ryder

Koribalski

Staveley‐Smith

et al. 2001

ApJ

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We report the discovery, from the HI Parkes All-Sky Survey (HIPASS), of a gas cloud associated with the asymmetric spiral galaxy NGC 2442. This object, designated HIPASS J0731-69, contains ~10^9 M_sun of HI, or nearly one-third as much atomic gas as NGC 2442 itself. No optical counterpart to any part of HIPASS J0731-69 has yet been identified, consistent with the gas being diffuse, and with its stream-like kinematics. If the gas in HIPASS J0731-69 was once part of NGC 2442, then it was most likely a fairly recent tidal encounter with a moderately massive companion which tore it loose, although the possibility of ram-pressure stripping cannot be ruled out. This discovery highlights the potential of the HIPASS data for yielding new clues to the nature of some of the best-known galaxies in the local universe.Comment: 8 pages, 4 figures, uses "emulateapj5.sty". Accepted for publication in ApJ, Vol. 555, 1 July 2001. Figs 1 and 2 included as JPE

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NGC 7421: Surfing the Intracluster Medium?

Cited by 21 publications

References 8 publications

On the origin of circular and hexagonal formations in galaxies

On the origin of circular and hexagonal formations in galaxies

HiObservations of Barred Magellanic Spirals. II. The Frequency and Impact of Companions

HIPASS Detection of an Intergalactic Gas Cloud in the NGC 2442 Group

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