Arcs and bridges in the interacting galaxies NGC 5775/NGC 5774

Irwin, Judith A.

doi:10.1086/174349

Cited by 83 publications

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“…The vertical emission profiles will be examined in Paper II; we merely point out for the current purposes that, for data averaged over 10 spatial pixels, the Ha intensity reaches peak values, in slits 1 and 2, respectively, of 1. (Irwin 1994) inclination of the galaxy, for points within 10Љ of the midplane ( pc in the z Շ 1200 figures), the spatial axis reflects in-plane, highly inclined disk structure rather than true height above the plane, and line ratio variations are more due to the line of sight crossing H ii regions and areas between them. This fact explains why line ratio minima are not always at kpc.…”

Section: Resultsmentioning

confidence: 99%

Ionization, Kinematics, and Extent of the Diffuse Ionized Gas Halo of NGC 5775

Rand

2000

The Astrophysical Journal

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We present key results from deep spectra of the diffuse ionized gas halo of the edge-on galaxy NGC 5775.[N ii] l6583 has been detected up to kpc above the plane in one of two vertically oriented long slits-making z ≈ 13 this the spiral galaxy with the greatest spectroscopically detected halo extent in emission. Key diagnostic line ratios have been measured up to kpc, allowing the source of ionization and physical state to be probed. z ≈ 8 Ionization by a dilute radiation field from massive stars in the disk can explain some of the line ratio behavior, but departures from this picture are clearly indicated, most strongly by the rise of [O iii]/Ha with z. Velocities of the gas in both slits approach the systemic velocity of the galaxy at several kiloparsecs above the plane. We interpret this trend as a decrease in rotation velocity with z, with essentially no rotation at heights of several kiloparsecs. Such a trend was observed in the edge-on galaxy NGC 891, but here much more dramatically. This falloff is presumably due to the gravitational potential changing with z, but will also depend on the hydrodynamic nature of the disk-halo cycling of gas and projection effects. More detailed modeling of the ionization and kinematics of this and other edge-ons will be presented in future papers.

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Section: Resultsmentioning

confidence: 99%

Ionization, Kinematics, and Extent of the Diffuse Ionized Gas Halo of NGC 5775

Rand

2000

The Astrophysical Journal

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“…New radio observations were made using the Very Large Array interferometer (VLA) of the A&A 531, A127 (2011) Dahlem et al (1995); b Irwin (1994). National Radio Astronomical Observatory (NRAO 1 ).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

The large scale magnetic field structure of the spiral galaxy NGC 5775

Soida

Krause

Dettmar

et al. 2011

A&A

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Context. The origin of large-scale magnetic fields in spiral galaxies is still a theoretical riddle and better observational constraints are required to make further progress. Aims. In order to better determine the large-scale 3D-structure of magnetic fields in spiral galaxies we present a Faraday rotation analysis of the edge-on spiral galaxy NGC 5775. Methods. Deep radio-continuum observations in total power and linear polarization were performed at 8.46 GHz with the VLA and the 100-m Effelsberg telescope. They were analyzed together with archival 4.86 and 1.49 GHz VLA-data. We thus can derive rotation measures from a comparison of three frequencies and determine the intrinsic magnetic field structure. Results. A very extended halo is detected in NGC 5775, with magnetic field lines forming an X-shaped structure. Close to the galactic disk the magnetic field is plane-parallel. The scaleheights of the radio emission esimated for NGC 5775 are comaprable with other galaxies. The rotation measure distribution varies smoothly on both sides along the major axis from positive to negative values. Conclusions. From the derived distribution of rotation measures and the plane-parallel intrinsic magnetic field orientation along the galactic midplane we conclude that NGC 5775 has an even axisymmetric large-scale magnetic field configuration in the disk as generated by an αΩ-dynamo which is accompanied by a quadrupolar poloidal field. The magnetic field lines of the plane-parallel component are pointing outwards. The observed X-shaped halo magnetic field, however, cannot be explained by the action of the disk's mean-field dynamo alone. It is probably due to the influence of the galactic wind together with the dynamo action.

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“…Duric and Bloemen (1989) detected an extended radio halo around NGC 5775, which is confirmed by data by Golla (1996, personal communication). Associated Ha from the halo was detected by Lehnert and Heckman (1996a) and several large HI arcs were found in NGC 5775 by Irwin (1994). Although interacting with its companion, NGC 5774, the optical appearance of NGC 5775 seems quite undisturbed and therefore the assumption appears to be justified that the halo emission (except possibly the H i) is not predominantly caused by tidal disturbances.…”

Section: Other Normal Edge-on Galaxiesmentioning

confidence: 99%

“…No relation has been found between the locations of the gaseous spurs and the local level of SF in those parts of the disks in which the filaments root. NGC 5775 is also interacting and at least the HI gas might be affected as well by tidal forces (Irwin 1994(Irwin , 1995. The H I of M82 is also affected by its interaction with M 81 (Yun et al 1994).…”

Section: Environmental Influencesmentioning

confidence: 99%

Gaseous Halos of Late-Type Spiral Galaxies

Dahlem¹

1997

PASP

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ABSTRACT. This article reviews the most recent observational results on disk-halo interactions in nearby galaxies. The implications of these results on our understanding of the structure of the interstellar medium (ISM) in our Galaxy and external spiral galaxies, with particular emphasis on the halo ISM, are discussed. Disk-halo interactions occur only above the brightest HII regions, which are found almost exclusively in late-type spirals and dwarf and irregular galaxies. Circumnuclear starbursts are the most energetic flavor of this phenomenon. The existence, the shapes, and the properties of gaseous halos depend on the level of energy input into the disk ISM per unit surface area, i.e., on the feedback of mass, momentum, and energy produced by vigorous star formation. Thus, current theoretical models of the ISM take into account that gaseous halos are natural extensions of disk ISMs and are heated by the winds and ionizing radiation of massive stars, and by the shock waves of Supernovae and their remnants. Observationally, this is reflected by the fact that all phases of the ISM known to exist in galaxy disks have also been detected in halos. Disk-halo interactions are a very effective way of redistributing energy, metals, and magnetic fields in galaxies and of expelling them into intergalactic space when outflows reach escape velocity. MOTIVATION AND OUTLINESpiral galaxies consist of three spatially and dynamically dinstinct components, namely bulge, disk, and halo. Of these, the central bulge consists primarily of old stars and has a low gas fraction. The disk and halo consist of stars plus gas, dust, and in many cases "dark matter." Here I want to concentrate on the interstellar medium (ISM) in the disks and halos of galaxies, with emphasis on late-type spirals. Massive dark halos will not be described (see, e.g., Ashman 1992; Holt and Bennett 1995). In the current context "latetype" stands for disk-dominated spirals with rather inconspicuous bulges (Hubble types Sb -Sdm). The ISM of elliptical galaxies and early-type spirals (S0-Sab) will also not be presented here (cf. Walsh et al. 1989;and Fabbiano 1989).Studies of the ISM contribute significantly to our understanding of the structure, kinematics, and evolution of galaxies. The level of star formation (SF), its spatial distribution, and its temporal changes depend strongly on the properties of the interstellar gas from which stars can form. Stars feed energy and metal-enriched matter back into the ambient medium via stellar winds and supernovae (SNe), thereby distributing processed material throughout the ISM. Hence, through this gas-star-gas cycle, the ISM becomes a mediator of SF.In Sec. 2, the different phases of the ISM in galaxies will be introduced, and Sec. 3 presents observations of the ISM in the Milky Way. Section 4 will show that the Galactic ISM is l A\\ correspondence should be directed to this address. not confined to the thin disk, but extends to high distances (z) above the plane, forming a gaseous halo. However, being located within the...

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Arcs and bridges in the interacting galaxies NGC 5775/NGC 5774

Cited by 83 publications

References 0 publications

Ionization, Kinematics, and Extent of the Diffuse Ionized Gas Halo of NGC 5775

Ionization, Kinematics, and Extent of the Diffuse Ionized Gas Halo of NGC 5775

The large scale magnetic field structure of the spiral galaxy NGC 5775

Gaseous Halos of Late-Type Spiral Galaxies

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