Stellar spiral arms in smooth-armed galaxies

Kennicutt, R. C.; Edgar, B. K.

doi:10.1086/163787

Cited by 11 publications

(9 citation statements)

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“…See Erwin & Sparke (2003). The break in the profile at ∼41 matches the outer pseudoring (studied by Kennicutt & Edgar 1986). Note that there is an additional, faint ring at larger radii, visible as a bump in the profile at r ∼ 70 .…”

Section: Note On Individual Galaxiessupporting

confidence: 68%

The Outer Disks of Early-Type Galaxies. I. Surface-Brightness Profiles of Barred Galaxies

Erwin

Pohlen

Beckman

2007

The Astronomical Journal

223

361

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We present a study of 66 barred, early-type (S0-Sb) disk galaxies, focused on the disk surface brightness profile outside the bar region, with the aim of throwing light on the nature of Freeman type I and II profiles, their origins, and their possible relation to disk truncations. This paper discusses the data and their reduction, outlines our classification system, and presents R-band profiles for all galaxies in the sample, along with their classifications. In subsequent papers, we will explore the structure of outer disks as revealed by these profiles, and investigate their possible origins. The profiles are derived from a variety of different sources, including the Sloan Digital Sky Survey (Data Release 5). For about half of the galaxies, we have profiles derived from more than one telescope; this allows us to check the stability and repeatability of our profile extraction and classification. The vast majority of the profiles are reliable down to levels of µ R ≈ 27 mag arcsec −2 ; in exceptional cases, we can trace profiles down to µ R > 28. We can typically follow disk profiles out to at least 1.5 times the traditional optical radius R 25 ; for some galaxies, we find light extending to ∼3×R 25 . For type I (single-exponential) profiles, this means that we can trace the exponential disk out to 6-7 scale lengths. We classify the profiles into three main groups: type I (single-exponential), type II (down-bending), and type III (up-bending). The frequencies of these types are approximately 27%, 42%, and 24%, respectively, plus another 6% which are combinations of types II and III. We further classify type II profiles by where the break falls in relation to the bar length, and in terms of the postulated mechanisms for breaks at large radii ("classical truncation" of star formation versus the influence of the Outer Lindblad Resonance of the bar). We also classify the type III profiles by the probable morphology of the outer light (disk or spheroid). Illustrations are given for all cases.

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Section: Note On Individual Galaxiessupporting

confidence: 68%

The Outer Disks of Early-Type Galaxies. I. Surface-Brightness Profiles of Barred Galaxies

Erwin

Pohlen

Beckman

2007

The Astronomical Journal

223

361

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“…Along the K-band arms in NGC 5248, there is good spatial coincidence between peaks in K-band emission and H ii regions as traced by Ha images. The patchy morphology of the K-band spirals is in stark contrast to the smooth appearance of old stellar arms (e.g., Kennicutt & Edgar 1986). Taken together, these properties suggest that young stars dominate the K-band spirals.…”

Section: Discussion: Implications For Barred Spirals Locally and At Hmentioning

confidence: 86%

Discovery and Implications of a New Large-Scale Stellar Bar in NGC 5248

Jogee

Knapen

Laine

et al. 2002

The Astrophysical Journal

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For decades, the grand-design SAB spiral galaxy NGC 5248 has been postulated to host a short bar of semimajor axis 22Љ (1.6 kpc). From dynamical and morphological arguments, however, we argue that its spiral structure is being driven by a large-scale bar whose corotation radius lies at ∼115Љ (8.6 kpc). Our estimate is based partially on a deep R-band image, which reveals that the feature previously thought to be an inclined disk is in fact an extended stellar bar. The bar is embedded within a fainter outer disk visible out to a radius of 230Љ (17.2 kpc). The bar has a deprojected ellipticity of 0.44 and a semimajor axis of 95Љ (7.1 kpc). The classical grand-design spirals of NGC 5248, prominent in B, R, and K light, lie on the leading edge of the large-scale stellar bar and are accompanied by concave dust lanes out to at least 70Љ. The offset between the dust and young stars is consistent with our understanding of gas flows in barred galaxies, where shocks along the leading edges of a moderately strong bar compress the gas to form massive young stars. While in many strongly barred galaxies, optical spiral arms are prominent outside the bar but not within it, NGC 5248 illustrates how intense star formation along a moderately strong bar can lead to conspicuous open spiral arms within the bar itself. NGC 5248 also provides a clear example of how a large-scale stellar bar embedded within a faint outer optical disk can be misidentified as an inclined disk when imaging studies lack the sensitivity to detect the actual outer disk. We discuss the implications for the estimated bar fraction at higher redshifts.

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“…There are two ways of estimating the contribution of young stars to the surface brightness enhancement in the spiral arms. First, because young stellar populations are both brighter and bluer than older ones, one can compare the arm/inter-arm color change to the arm/inter-arm brightness contrast (Schweizer, 1976;Jensen, Talbot and Dufour, 1981;Elmegreen and Elmegreen, 1984;Kennicutt and Edgar, 1986). These authors demonstrate that the color change across the spiral arm is too small to explain the brightness contrast merely through azimuthal mass-to-light ratio variations; consequently they argue for a substantial enhancement of the stellar surface mass density in the spiral arms of grand design spirals.…”

Section: Surface Brightness Vs Surface Mass Densitymentioning

confidence: 99%

Nonaxisymmetric Structures in the Stellar Disks of Galaxies

Rix¹,

Zaritsky²

1995

ApJ

345

428

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We study the azimuthal structure of the stellar disks of 18 face-on spiral galaxies, using K 0 (2:2 m)band photometry to trace the stellar surface mass density. Assuming the disks are co-planar, we characterize their deviation from axisymmetry by the fractional amplitudes, A m (R)=A 0 (R), and phases, ' m (R), of the m th azimuthal Fourier components at radii R about the photometric galaxy center. We nd that most disks exhibit a wealth of non-axisymmetric structures, speci cally: (1) that about one third of them are substantially lopsided (A 1 =A 0 > 0:20) at 2.5 disk exponential scale length, (2) that almost one half of them have strong two-armed spirals with an arm/interarm surface-brightness contrasts of order unity, and (3) that typical disks have some intrinsic ellipticity. We estimate that in the disk plane the characteristic ellipticity of the underlying potential is 0:045 +0:03 0:02 . However, the spiral pattern couples signi cantly to the estimate of the intrinsic ellipticity, and our measurement may represent an upper limit on the \true" potential triaxiality. We estimate the radial streaming motions of the disk stars, v R , which are produced by these distortions.By averaging over our sample of galaxies and all azimuthal angles, we nd hv R i 7 km s 1 due to lopsided distortions and hv R i 6 km s 1 due to intrinsic ellipticity. These non-circular motions are expected to contribute 0:15mags scatter to measurements of the Tully-Fisher relation.

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Stellar spiral arms in smooth-armed galaxies

Cited by 11 publications

References 0 publications

The Outer Disks of Early-Type Galaxies. I. Surface-Brightness Profiles of Barred Galaxies

The Outer Disks of Early-Type Galaxies. I. Surface-Brightness Profiles of Barred Galaxies

Discovery and Implications of a New Large-Scale Stellar Bar in NGC 5248

Nonaxisymmetric Structures in the Stellar Disks of Galaxies

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