A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies

Details A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies

2003-05-22

arxiv.org/abs/astro-ph/0305427v1

Astron.J. 126 (2003) 1148

Astronomy and Astrophysics

Astrophysics

15 pages latex, including 6 postscript figures (Fig. 5 in colour). Revised version submitted to AJ

Scientific paper

10.1086/377316

We describe a Fourier-based method of separating bars from spirals in near-infrared images. The method takes advantage of the fact that a bar is typically a feature with a relatively fixed position angle, and uses the simple assumption that the relative Fourier amplitudes due to the bar decline with radius past a maximum in the same or a similar manner as they rose to that maximum. With such an assumption, the bar can be extrapolated into the spiral region and removed from an image, leaving just the spiral and the axisymmetric background disk light. The procedure allows us to estimate the maximum gravitational torque per unit mass per unit square of the circular speed for the bar and spiral forcing separately, parameters which quantitatively define the bar strength Q_b and the spiral strength Q_s following the recent study of Buta & Block. We outline the complete procedure here using a 2.1 micron image of NGC 6951, a prototypical SAB(rs)bc spiral. We justify our assumption on how to make the bar extrapolation using an analysis of NGC 4394, a barred spiral with only weak near-infrared spiral structure, and we justify the number of needed Fourier terms using NGC 1530, one of the most strongly-barred galaxies (bar class 7) known. We also evaluate the main uncertainties in the technique. Allowing for uncertainties in vertical scaleheight, bar extrapolation, sky subtraction, orientation parameters, and the asymmetry in the spiral arms themselves, we estimate Q_b=0.28\pm0.04 and Q_s=0.21\pm0.06 for NGC 6951. (abridged)

Affiliated with

Also associated with

No associations

Rating

A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-40766