Analysis of Resonances in Grand Design Spiral Galaxies

Vera-Villamizar, N.; Dottori, H.; Puerari, I.; Carvalho, R. R. de

doi:10.1086/318362

Cited by 22 publications

(19 citation statements)

References 18 publications

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“…These values of Ω p are slightly lower than previous estimates (Grosbøl et al 1999;Vera-Villamizar et al 2001). The standard SB99 models do not account for Q values above 0.4 mag as observed and may not predict the NIR colors of the youngest, most massive clusters well (possibly due to circumstellar emission).…”

Section: Pattern Speed Of Spiralscontrasting

confidence: 67%

Pattern speed of main spiral arms in NGC 2997

Grosbøl¹,

Dottori²

2009

A&A

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Context. Bright knots along arms are observed in K-band images of many grand-design spiral galaxies. They are identified as young starforming complexes using K-band spectra which show strong Br γ emission. Their alignment with spiral arms and ages <10 Myr suggest that they are associated with a starforming front linked to a density wave in the galaxies. Aims. Ages may be estimated for the youngest starforming complexes using NIR broad band colors and Br γ . A different angular speed of the density wave and material would lead to an azimuthal age gradient of newly formed objects. We aim to detect this gradient. Methods. Deep JHK-Br γ photometry of the southern arm of the grand-design spiral galaxy NGC 2997 was obtained by ISAAC/VLT. All sources in the field brighter than K = 19 mag were located. Color−color diagrams were used to identify young stellar complexes among the extended sources. Ages can be estimated for the youngest complexes and correlated with azimuthal distances from the spiral arms defined by the K-band intensity variation. Results. The extended sources with M K < −12 mag display a diffuse appearance and are more concentrated inside the arm region than fainter ones, which are compact and uniformly distributed in the disk. The NIR colors of the bright diffuse objects are consistent with them being young starforming complexes with ages <10 Myr and reddened by up to 8 mag of visual extinction. They show a color gradient as a function of their azimuthal distance from the spiral arms. Interpreting this gradient as an age variation, the pattern speed Ω p = 16 km s −1 kpc −1 of the main spiral was derived assuming circular motion. Conclusions. The alignment and color gradient of the bright, diffuse complexes strongly support a density wave scenario for NGC 2997. Only the brightest complexes with M K < −12 mag show a well aligned structure along the arm, suggesting that a strong compression in the gas due to the spiral potential is required to form these most massive aggregates, while smaller starforming regions are formed more randomly in the disk. The sharp transition between the two groups at M K = −12 mag may be associated with expulsion of gas when the first supernovae explode in the complex.

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Section: Pattern Speed Of Spiralscontrasting

confidence: 67%

Pattern speed of main spiral arms in NGC 2997

Grosbøl¹,

Dottori²

2009

A&A

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“…The spiral structures traced by blue, young stars are particularly obvious on the color composite image, and also on the Hα image as strings of prominent star-forming regions. Indeed, the previous imaging study by Vera-Villamizar et al (2001) has found m = 2 and m = 3 modes in NGC 2997. We define spiral arms by visually identifying strings of bright knots on the Hα map whose spatial distribution can be approximately described by the logarithmic spiral formula,…”

Section: Spiral Arm Maskmentioning

confidence: 86%

Azimuthal variations of gas-phase oxygen abundance in NGC 2997

Meidt

Kudritzki

et al. 2018

A&A

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The azimuthal variation of the H ii region oxygen abundance in spiral galaxies is a key observable for understanding how quickly oxygen produced by massive stars can be dispersed within the surrounding interstellar medium. Observational constraints on the prevalence and magnitude of such azimuthal variations remain rare in the literature. Here, we report the discovery of pronounced azimuthal variations of H ii region oxygen abundance in NGC 2997, a spiral galaxy at approximately 11.3 Mpc. Using 3D spectroscopic data from the TYPHOON Program, we study the H ii region oxygen abundance at a physical resolution of 125 pc. Individual H ii regions or complexes are identified in the 3D optical data and their strong emission line fluxes measured to constrain their oxygen abundances. We find 0.06 dex azimuthal variations in the oxygen abundance on top of a radial abundance gradient that is comparable to those seen in other star-forming disks. At a given radial distance, the oxygen abundances are highest in the spiral arms and lower in the inter-arm regions, similar to what has been reported in NGC 1365 using similar observations. We discuss whether the azimuthal variations could be recovered when the galaxy is observed at worse physical resolutions and lower signal-to-noise ratios.

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“…This technique has frequently been used in the past to quantify non-axisymmetric structures in disk galaxies (Grosbol 1987;Elmegreen et al 1989;Rix & Zaritsky 1995;Vera-Villamizar et al 1998). We used the Fourier expansion in the polar form, with azimuthal angle Θ.…”

Section: Residual Images and Fourier Expansionmentioning

confidence: 99%

More evidence for hidden spiral and bar features in bright early-type dwarf galaxies

Barazza

Binggeli

Jerjen

2002

A&A

130

165

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Abstract. Following the discovery of spiral structure in IC 3328 (Jerjen et al. 2000), we present further evidence that a sizable fraction of bright early-type dwarfs in the Virgo cluster are genuine disk galaxies, or are hosting a disk component. Among a sample of 23 nucleated dwarf ellipticals and dS0s observed with the Very Large Telescope in B and R, we found another four systems exhibiting non-axisymmetric structures, such as a bar and/or spiral arms, indicative of a disk (IC 0783, IC 3349, NGC 4431, IC 3468). Particularly remarkable are the two-armed spiral pattern in IC 0783 and the bar and trailing arms in NGC 4431. For both galaxies the disk nature has recently been confirmed by a rotation velocity measurement (Simien & Prugniel 2002). Our photometric search is based on a Fourier decomposition method and a specific version of unsharp masking. Some "early-type" dwarfs in the Virgo cluster seem to be former late-type galaxies which were transformed to early-type morphology, e.g. by "harassment", during their infall to the cluster, while maintaining part of their disk structure.

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Analysis of Resonances in Grand Design Spiral Galaxies

Cited by 22 publications

References 18 publications

Pattern speed of main spiral arms in NGC 2997

Pattern speed of main spiral arms in NGC 2997

Azimuthal variations of gas-phase oxygen abundance in NGC 2997

More evidence for hidden spiral and bar features in bright early-type dwarf galaxies

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