Testing Density Wave Theory with Stellar Populations around Spiral - PowerPoint PPT Presentation

Testing Density Wave Theory with Stellar Populations around Spiral Arms in M81 Yumi Choi 1 Julianne J. Dalcanton 1 , Benjamin F. Williams 1 , and Daniel Weisz 2 1 University of Washington, 2 UC Santa Cruz

Relationship between Spiral Arms and SF NGC 6946 Q: What is the role of spiral pattern in SF?

Density Wave Theory CO emission traces cold, dense molecular gas Pearson education, Inc.

Density Wave Theory CO emission traces cold, dense molecular gas 24 μ m emission traces obscured SF Pearson education, Inc.

Density Wave Theory CO emission traces cold, dense molecular gas 24 μ m emission traces obscured SF H α , UV traces young stars Pearson education, Inc.

Density Wave Theory CO emission traces cold, dense molecular gas 24 μ m emission traces obscured SF H α , UV traces young stars Evolved stars Pearson education, Inc.

How to Detect/Quantify this? — Angular offsets among SF tracers tracing different stages of SF (e.g.) Tamburro et al. (2008), Egusa et al. (2009), Foyle et al. (2011) — Color gradient (e.g.) Martínez-García et al. (2013) — Age distribution of star clusters (e.g.) Santiago-Cortés et al. (2010), Grosbøl et al. (2012) — Resolved stellar populations

Recover SFH using CMD fitting Magnitude Color

Recover SFH using CMD fitting Observation Model 20 20 20 20 20 22 22 22 22 22 F435W F435W F435W F435W F435W 24 24 24 24 24 26 26 26 26 26 0 0 1 1 2 2 3 3 0 0 0 1 1 1 2 2 2 3 3 3 F435W-F606W F435W-F606W F435W-F606W F435W-F606W F435W-F606W

Grand-design Spiral M81 PA = 330° & Inclination = 59° (de Blok et al. 2008) Ω p ~ 17 km/s/kpc & R CO ~ 12-13 kpc (Kendall et al. 2008)

M81 Group M82 M81 NGC 3077 Jordi Gallego

Tidal Interactions in M81 group M82 M81 N 3077 Yun et al. (1994, 1999)

Optical & HI DATA — 29 ACS fields - F435W(B) & F606W(V) — HI map from THINGS (Walter et al. 2008)

Identify Spiral Arms Rad 1 Rad 4 Rad 2 Rad 3 ~2.8 kpc

Recovered SFHs Inner Outer Trailing Leading

Recovered SFHs Inner Outer Trailing Tidally induced SF? Leading

SF Propagation Rad 1 9 13 Red box = expected propagation of SF

SF Propagation Rad 2

SF Propagation Rad 3

SF Propagation Rad 4

Conclusions — No predicted trends detected in M81 - resolved stellar populations inconsistent with other results? - no systematic spatial ordering between SF tracers (Foyle et al. 2011) — Complexities - not a single pattern speed - scattering by stellar feedback - highly embedded stars, etc.,…

Thanks! Yumi Choi