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Radial dependence of the pattern speed of M51

(2008) ASTROPHYSICAL JOURNAL. 688(1). p.224-236
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Abstract
The grand-design spiral galaxy M51 has long been a crucial target for theories of spiral structure. Studies of this iconic spiral can address the question of whether strong spiral structure is transient (e. g., interaction-driven) or long-lasting. As a clue to the origin of the structure in M51, we investigate evidence for radial variation in the spiral pattern speed using the radial Tremaine-Weinberg (TWR) method. We implement the method on CO observations tracing the ISM-dominant molecular component. Results from the method's numerical implementation-combined with regularization, which smooths intrinsically noisy solutions-indicate two distinct patterns speeds inside 4 kpc at our derived major axis P.A. = 170 degrees, both ending at corotation and both significantly higher than the conventionally adopted global value. Inspection of the rotation curve suggests that the pattern speed interior to 2 kpc lacks an ILR, consistent with the leading structure seen in HST near-IR observations. We also find tentative evidence for a lower pattern speed between 4 and 5.3 kpc measured by extending the regularized zone. As with the original TW method, uncertainty in major axis position angle (P. A.) is the largest source of error in the calculation; in this study, where delta(P.A.) = +/- 5 degrees, a similar to 20% error is introduced to the parameters of the speeds at P.A. = 170 degrees. Accessory to this standard uncertainty, solutions with P.A. = 175 degrees (also admitted by the data) exhibit only one pattern speed inside 4 kpc, and we consider this circumstance under the semblance of a radially varying P.A.
Keywords
TREMAINE-WEINBERG METHOD, N-BODY MODEL, SPIRAL STRUCTURE, BARRED, GALAXIES, DISK GALAXIES, DENSITY-WAVE, STAR-FORMATION, GRAND DESIGN, H-ALPHA, KINEMATICS, galaxies: kinematics and dynamics, galaxies: spiral, galaxies: structure, methods: numerical

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Citation

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MLA
van der Wel, Sharon Meidt, et al. “Radial Dependence of the Pattern Speed of M51.” ASTROPHYSICAL JOURNAL, vol. 688, no. 1, 2008, pp. 224–36.
APA
van der Wel, S. M., Rand, R. J., Merrifield, M. R., Shetty, R., & Vogel, S. N. (2008). Radial dependence of the pattern speed of M51. ASTROPHYSICAL JOURNAL, 688(1), 224–236.
Chicago author-date
Wel, Sharon Meidt van der, Richard J Rand, Michael R Merrifield, Rahul Shetty, and Stuart N Vogel. 2008. “Radial Dependence of the Pattern Speed of M51.” ASTROPHYSICAL JOURNAL 688 (1): 224–36.
Chicago author-date (all authors)
van der Wel, Sharon Meidt, Richard J Rand, Michael R Merrifield, Rahul Shetty, and Stuart N Vogel. 2008. “Radial Dependence of the Pattern Speed of M51.” ASTROPHYSICAL JOURNAL 688 (1): 224–236.
Vancouver
1.
van der Wel SM, Rand RJ, Merrifield MR, Shetty R, Vogel SN. Radial dependence of the pattern speed of M51. ASTROPHYSICAL JOURNAL. 2008;688(1):224–36.
IEEE
[1]
S. M. van der Wel, R. J. Rand, M. R. Merrifield, R. Shetty, and S. N. Vogel, “Radial dependence of the pattern speed of M51,” ASTROPHYSICAL JOURNAL, vol. 688, no. 1, pp. 224–236, 2008.
@article{8622911,
  abstract     = {The grand-design spiral galaxy M51 has long been a crucial target for theories of spiral structure. Studies of this iconic spiral can address the question of whether strong spiral structure is transient (e. g., interaction-driven) or long-lasting. As a clue to the origin of the structure in M51, we investigate evidence for radial variation in the spiral pattern speed using the radial Tremaine-Weinberg (TWR) method. We implement the method on CO observations tracing the ISM-dominant molecular component. Results from the method's numerical implementation-combined with regularization, which smooths intrinsically noisy solutions-indicate two distinct patterns speeds inside 4 kpc at our derived major axis P.A. = 170 degrees, both ending at corotation and both significantly higher than the conventionally adopted global value. Inspection of the rotation curve suggests that the pattern speed interior to 2 kpc lacks an ILR, consistent with the leading structure seen in HST near-IR observations. We also find tentative evidence for a lower pattern speed between 4 and 5.3 kpc measured by extending the regularized zone. As with the original TW method, uncertainty in major axis position angle (P. A.) is the largest source of error in the calculation; in this study, where delta(P.A.) = +/- 5 degrees, a similar to 20% error is introduced to the parameters of the speeds at P.A. = 170 degrees. Accessory to this standard uncertainty, solutions with P.A. = 175 degrees (also admitted by the data) exhibit only one pattern speed inside 4 kpc, and we consider this circumstance under the semblance of a radially varying P.A.},
  author       = {van der Wel, Sharon Meidt and Rand, Richard J and Merrifield, Michael R and Shetty, Rahul and Vogel, Stuart N},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {TREMAINE-WEINBERG METHOD,N-BODY MODEL,SPIRAL STRUCTURE,BARRED,GALAXIES,DISK GALAXIES,DENSITY-WAVE,STAR-FORMATION,GRAND DESIGN,H-ALPHA,KINEMATICS,galaxies: kinematics and dynamics,galaxies: spiral,galaxies: structure,methods: numerical},
  language     = {eng},
  number       = {1},
  pages        = {224--236},
  title        = {Radial dependence of the pattern speed of M51},
  url          = {http://dx.doi.org/10.1086/591516},
  volume       = {688},
  year         = {2008},
}

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