The Westerbork SINGS survey

Braun, Róbert; Oosterloo, Tom; Morganti, Raffaella; Klein, U.; Beck, Rainer

doi:10.1051/0004-6361:20066092

Cited by 87 publications

(116 citation statements)

References 56 publications

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“…In model 6 this fraction is somewhat lower (75%). Both have beam-averaged H 2 column densities N H 2 ≈ 5 × 10 21 cm −2 which is very similar to the peak HI column density listed by Braun et al (2007). These column densities are relatively high but this is not surprising given the edge-on orientation of the galaxy.…”

Section: Ngc 3628supporting

confidence: 71%

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 3628supporting

confidence: 71%

CI and CO in nearby galaxy centers

Israel¹

2009

A&A

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“…For the other, only the XX-and YY-correlations were available. From this data, only a total power image of the 18 cm dataset has been published so far by Braun et al (2007).…”

Section: Westerbork Observationsmentioning

confidence: 99%

“…15). An additional measurement could be acquired from Braun et al (2007) for the core region, but the dynamic range of their maps was not sufficient to extract a measurement for the halo.…”

Section: Disentangling the Core And Halo Emissionmentioning

confidence: 99%

M 82 – A radio continuum and polarisation study

Adebahr

Krause

Klein

et al. 2013

A&A

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104

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Context. The potential role of magnetic fields and cosmic ray propagation for feedback processes in the early Universe can be probed by studies of local starburst counterparts with an equivalent star-formation rate. Aims. In order to study the cosmic ray propagation and determine the magnetic field strength and dominant loss processes in the nearby prototypical starbursting galaxy M 82, a multi-frequency analysis at four radio wavelengths is presented. Methods. Archival data from the Westerbork Synthesis Radio Telescope (WSRT) was reduced and a new calibration technique introduced to reach the high dynamic ranges needed for the complex source morphology. These data were combined with archival Very Large Array (VLA) data, yielding total power maps at λ3 cm, λ6 cm, λ22 cm, and λ92 cm. Results. The data show a confinement of the emission at wavelengths of λ3/λ6 cm to the core region and a largely extended halo reaching up to 4 kpc away from the galaxy midplane at wavelengths of λ22/λ92 cm up to a sensitivity limit of 90 µJy and 1.8 mJy respectively indicating different physical processes in the core and halo regions. The results are used to calculate the magnetic field strength to 98 µG in the core region and to 24 µG in the halo regions. From the observation of ionisation losses, the filling factor of the ionised medium could be estimated to 2%. This leads to a revised view of the magnetic field distribution in the core region and the propagation processes from the core into the halo regions. Conclusions. We find that the radio emission from the core region is dominated by very dense H -regions and supernova remnants, while the surrounding medium is filled with hot X-ray and neutral gas. Cosmic rays radiating at frequencies higher than 1.4 GHz suffer from high synchrotron and inverse Compton losses in the core region and are not able to reach the halo. Even the cosmic rays radiating at longer wavelengths are only able to build up the observed kpc-sized halo, when several starbursting periods are assumed where the far-infrared and radio luminosity vary by an order of magnitude. These findings, together with the strong correlation between Hα, ionised polycyclic aromatic hydrocarbons (PAH + ), and our radio continuum data, suggest a magnetic field which is frozen into the ionised medium and driven out of the galaxy kinematically.

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“…The flux density at 1.365 GHz was taken from Braun et al (2007) and at 10.55 GHz from Dumke et al (1995). These values were incorporated because they are the most recent total flux-densities published of NGC 4631.…”

Section: Total and Nonthermal Spectral Indicesmentioning

confidence: 99%

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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The Westerbork SINGS survey

Cited by 87 publications

References 56 publications

CI and CO in nearby galaxy centers

CI and CO in nearby galaxy centers

M 82 – A radio continuum and polarisation study

Magnetic field structure and halo in NGC 4631

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