Spiral structure of M51 - Thermal and nonthermal emission

Tilanus, Rpj; Allen, R. J.; Vanderhulst, Jm; Crane, P.; Kennicutt, R.

doi:10.1086/166502

Cited by 29 publications

(24 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1d of Aalto et al 1999). On close examination, some subtle differences can be seen, such as a shift between maxima in the CO and H i distributions, as discussed by Tilanus et al (1988). These displacements were interpreted by those authors as evidence that the H i is formed by photodissociation of the molecular gas by hot stars located even farther downstream in the spiral pattern.…”

Section: à2mentioning

confidence: 78%

Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law

Kennicutt

Calzetti

Walter

et al. 2007

ApJ

504

646

View full text Add to dashboard Cite

We have studied the relationship between the star formation rate (SFR), surface density, and gas surface density in the spiral galaxy M51a ( NGC 5194), using multiwavelength data obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS ). We introduce a new SFR index based on a linear combination of H emission-line and 24 m continuum luminosities, which provides reliable extinction-corrected ionizing fluxes and SFR densities over a wide range of dust attenuations. The combination of these extinction-corrected SFR densities with aperture synthesis H i and CO maps has allowed us to probe the form of the spatially resolved star formation law on scales of 0.5Y2 kpc. We find that the resolved SFR versus gas surface density relation is well represented by a Schmidt power law, which is similar in form and dispersion to the disk-averaged Schmidt law. We observe a comparably strong correlation of the SFR surface density with the molecular gas surface density, but no significant correlation with the surface density of atomic gas. The best-fitting slope of the Schmidt law varies from N ¼ 1:37 to 1.56, with zero point and slope that change systematically with the spatial sampling scale. We tentatively attribute these variations to the effects of areal sampling and averaging of a nonlinear intrinsic star formation law. Our data can also be fitted by an alternative parameterization of the SFR surface density in terms of the ratio of gas surface density to local dynamical time, but with a considerable dispersion.

show abstract

Section: à2mentioning

confidence: 78%

Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law

Kennicutt

Calzetti

Walter

et al. 2007

ApJ

504

646

View full text Add to dashboard Cite

show abstract

“…Tilanus et al (1988), using observations at a higher resolution, found that the shape of cross‐sectional profiles across the radio intensity arms is not compatible with the density wave theory and concluded that the synchrotron emitting interstellar medium is not compressed by shocks and decouples from the molecular clouds as it traverses the arms. Thus there is clearly a discrepancy between the physically appealing theory of Roberts & Yuan (1970) and observations (see also Condon 1992, p. 590).…”

Section: Arm–interarm Contrastsmentioning

confidence: 97%

Magnetic fields and spiral arms in the galaxy M51

Fletcher

Beck

Shukurov

et al. 2011

Monthly Notices of the Royal Astronomical Society

275

396

View full text Add to dashboard Cite

(Abridged) We use new multi-wavelength radio observations, made with the VLA and Effelsberg telescopes, to study the magnetic field of the nearby galaxy M51 on scales from $200\pc$ to several $\kpc$. Interferometric and single dish data are combined to obtain new maps at \wwav{3}{6} in total and polarized emission, and earlier \wav{20} data are re-reduced. We compare the spatial distribution of the radio emission with observations of the neutral gas, derive radio spectral index and Faraday depolarization maps, and model the large-scale variation in Faraday rotation in order to deduce the structure of the regular magnetic field. We find that the \wav{20} emission from the disc is severely depolarized and that a dominating fraction of the observed polarized emission at \wav{6} must be due to anisotropic small-scale magnetic fields. Taking this into account, we derive two components for the regular magnetic field in this galaxy: the disc is dominated by a combination of azimuthal modes, $m=0+2$, but in the halo only an $m=1$ mode is required to fit the observations. We disuss how the observed arm-interarm contrast in radio intensities can be reconciled with evidence for strong gas compression in the spiral shocks. The average arm--interam contrast, representative of the radii $r>2\kpc$ where the spiral arms are broader, is not compatible with straightforward compression: lower arm--interarm contrasts than expected may be due to resolution effects and \emph{decompression} of the magnetic field as it leaves the arms. We suggest a simple method to estimate the turbulent scale in the magneto-ionic medium from the dependence of the standard deviation of the observed Faraday rotation measure on resolution. We thus obtain an estimate of $50\pc$ for the size of the turbulent eddies.Comment: 21 pages, 18 figures (some at lower resolution than submitted version), accepted for publication in MNRA

show abstract

“…Generally, the strongest CO emission is seen to coincide with the dust lanes and non‐thermal ridges, in M51 for example (Lo et al 1987), and all of these are displaced from the peak of Hα emission (Tilanus et al 1988; Nakai et al 1994). The offset from CO peaks to H ii regions is seen in most grand design spirals, such as M31 (Ichikawa et al 1985).…”

Section: Spiral Arm Components and The Offset Functionmentioning

confidence: 99%

Constraining corotation from shocks in tightly wound spiral galaxies

Gittins¹,

Clarke²

2004

Monthly Notices of the Royal Astronomical Society

106

View full text Add to dashboard Cite

We present a new method for estimating the corotation radius in tightly wound spiral galaxies, through analysis of the radial variation of the offset between arms traced by the potential (P‐arms) and those traced by dust (D‐arms). We have verified the predictions of semi‐analytical theory through hydrodynamical simulations and have examined the uniqueness of the galactic parameters that can be deduced by this method. We find that if the range of angular offsets measured at different radii in a galaxy is greater than around π/4, it is possible to locate the radius of corotation to within ∼25 per cent. We argue that the relative location of the P‐ and D‐arms provides more robust constraints on the galactic parameters than can be inferred from regions of enhanced star formation (SF‐arms), as interpretation of the latter involves uncertainties due to reddening and the assumed star formation law. We thus stress the importance of K‐band studies of spiral galaxies.

show abstract

Spiral structure of M51 - Thermal and nonthermal emission

Cited by 29 publications

References 0 publications

Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law

Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law

Magnetic fields and spiral arms in the galaxy M51

Constraining corotation from shocks in tightly wound spiral galaxies

Contact Info

Product

Resources

About