Warm ionized gas in the edge-on galaxies NGC 4565 and NGC 4631

Rand, R.; Kulkarni, [No Value]; Hester, J.

doi:10.1086/171699

Cited by 71 publications

(84 citation statements)

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“…All this and the fact that the scale heights are significantly larger than usual, supports the view that convection may be strong in NGC 4631. Rand et al (1992) draw the same conclusion from their Hα observations. The Hα emission is very irregular and disturbed with a patchy high-z structure.…”

Section: Discussionsupporting

confidence: 69%

Magnetic field structure and halo in NGC 4631

Mora

Krause

2013

A&A

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Context. All of the edge-on spiral galaxies observed so far present a similar magnetic field configuration, which consists of a planeparallel field in the disk and an X-shaped field at larger z-distances from the plane of the galaxy. Only NGC 4631 seems to have a different field orientation in its disk. Along the eastern and western halves of the disk of NGC 4631 the magnetic field orientation is parallel to the galactic plane, but in the central region of the disk a vertical field seems to dominate. Aims. In order to clarify whether NGC 4631 has a unique magnetic field configuration in the central region along its disk, we present high-resolution Faraday-corrected polarization data. Methods. Radio continuum observations of NGC 4631 at 4.85 GHz were performed with the VLA. In addition, observations were made with the Effelsberg telescope at 4.85 GHz and at 8.35 GHz. These were analyzed together with archival VLA-data at 8.35 GHz. The single-dish and interferometer data were combined to recover the missing zero-spacings. Results. We determined an integrated total spectral index of α tot = −0.78 ± 0.04 and a nonthermal integrated spectral index of α nth = −0.87 ± 0.03. The vertical scale heights in NGC 4631 vary significantly in different regions within the galaxy and their mean values at 4.85 GHz are with 2.3 kpc (370 pc) for the thick (thin) disk higher than the mean values found so far in six other edge-on spiral galaxies. This may originate in the tidal interaction of NGC 4631 with its neighbouring galaxies. The rotation measures are characterized by a smooth large-scale distribution. Along the galactic plane the degree of Faraday depolarization is significantly high. We estimated a total magnetic field strength in the disk of NGC 4631 of B t ≈ 9 ± 2 μG and an ordered field strength of B ord ≈ 2 ± 1 μG. The total field strengths in the halo are of the order of the total magnetic field strength in the disk, whereas the ordered field strengths in the halo seem to be higher than the value in the disk. Conclusions. The derived distribution of rotation measures implies that NGC 4631 has a large-scale regular magnetic field configuration. Despite the strong Faraday depolarization along the galactic plane and the strong beam depolarization in the transition zone between the disk and halo, our research strongly indicates that the magnetic field orientation along the central 5-7 kpc of the disk is also plane-parallel. Therefore, we claim that NGC 4631 also has a magnetic field structure plane-parallel along its entire disk, similar to all other edge-on galaxies observed up to now.

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Section: Discussionsupporting

confidence: 69%

Magnetic field structure and halo in NGC 4631

Mora

Krause

2013

A&A

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“…The latter identified a radio continuum spur reaching from the brightest SF region in the central disk plane into the northern halo of NGC 4631, up to a z distance of -10 kpc. In addition, both diffuse and filamentary Ha was detected in the halo (Rand et al 1992;. NGC 4631 also has an extended hot gaseous halo, which was imaged by Wang et al (1995) and .…”

Section: Ngc 4631mentioning

confidence: 96%

“…eDIG: Optical line emission from eDIG was found out to -4.5 kpc (Dettmar 1990;Rand et al 1990). Part of the Ha emission is filamentary, while some of it might be genuinely diffuse; the heating source of this gas is not yet completely understood.…”

Section: Other Edge-on Starburst Galaxiesmentioning

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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“…Dettmar (1992) has published a good review paper on the subject. Other characteristics include a [Snj/Ha ratio of 0.3 off the disk and 0.1 in the galactic midplane, probably due to effects of photoionization in diffuse radiation fields (Rand 1994;Dettmar 1992;Rand et al 1990). …”

Section: The Warm Diffuse Ionized Gas In the Interstellar Mediummentioning

confidence: 99%

“…where T is typically 10,000 K for a WIM region and S Ha is the surface brightness in Ha emission in the region in ergs cm -2 s -1 sr -1 (Rand et al 1990). …”

Section: Observations Of Ngc 4244 and Ngc 5907mentioning

confidence: 99%

Increasing a Telescope's Field of View, and Subsequent Observations of Edge-On Galaxies NGC 4244 and NGC 5907

Marcus

1997

PASP

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ABSTRACT. A unique focal reducer for the Steward Observatory 2.3-m Ritchey-Chretien telescope on Kitt Peak was designed and built. It increased the field of view on a Loral 2048X2048 charged-coupled device (CCD) with 15 fim pixels from about 5' X5' to 24'X24'. The inverted-Cassegrainian, two-mirror design permits high efficiency of UV wavelengths and good broad-band image quality from 3500 to 8500 Â without significant chromatic aberrations. Other features include a coronagraph and a filter slide in the slow //9 beam which achieves the difficult and useful combination of narrow-band imaging with a wide field of view. The filter slide tilts to vary the center wavelength of narrow interference filters to accommodate different red shifts. The image quality is seeing-limited in the central 12' diameter, and degraded by about 0'.'8 in the central 18' diameter, and degraded by l"-2" at the edges of the field. The development of the optical system prescription is briefly discussed. The instrument is used to obtain continuum-corrected Ha and [S n] images of the edge-on galaxies NGC 4244 and NGC 5907. Interesting filamentary structure is evident. The distribution of ionized hydrogen gas in NGC 4244 and NGC 5907 is quantified. The data indicate those galaxies do not have an extended halo like that in NGC 891 and our Galaxy.

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Warm ionized gas in the edge-on galaxies NGC 4565 and NGC 4631

Cited by 71 publications

References 0 publications

Magnetic field structure and halo in NGC 4631

Magnetic field structure and halo in NGC 4631

Gaseous Halos of Late-Type Spiral Galaxies

Increasing a Telescope's Field of View, and Subsequent Observations of Edge-On Galaxies NGC 4244 and NGC 5907

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