Can Star Cluster Ages be Used to Answer Questions About Spurs/Feathers in M51 Brad Whitmore I age-date clusters for a living. Would this be useful in the context of this workshop

cat 4a- (2.9 Myr) cat 4b - (5.8 Myr) cat 3 - (2.0 Myr) cat 4b - (6.0 Myr) cat 3 - (2.4 Myr) cat 5- (400 Myr) cat 3 - (1.0 Myr) cat 2b - (1.0 Myr) H_alpha morphology can be used to age date clusters for ages < 10 Myr Categories below based on H_alpha morphology (i.e. coincident with cluster, small bubble, large bubble) Numerical ages below based on detailed UBVIH_alpha SED fitting. This is out in the “tidal” tail/arm near the companion. NOTE - Work in progress. All ages still tentative.

Another region (“pearl”) in one of the inner spiral arms H_alpha Age estimates I-band cat 5a - (10 Myr) cat 4b- (3.6 Myr) cat 3 - (1 Myr) cat 4b - (7.2 Myr) Star cat 2 - ( --- Myr) cat 3 - (1 Myr) cat 4a - (2.5 Myr) cat 4a - (1 Myr)

Color coding for circles blue green yellow red Region on edge of spiral arm nearest companion NOTE - Work in progress. All ages still tentative.

cat 4a - (3.3 Myr) cat 4a - (6.6 Myr) cat 4b - (6.9 Myr) cat 4a- (3.5 Myr) cat 5b - (102 Myr) cat 5a - (58 Myr) cat 4b- (6.0 Myr) cat 3 - (1 Myr) cat 4a - (5.5 Myr) cat 4a - (1.1 Myr) cat 4a - (2.9 Myr) cat 4a - (8.7 Myr) cat 5a - (115 Myr) cat 5a - (6.9 Myr) cat 5a - (19 Myr) cat 5a - (204 Myr) cat 5a- (72 Myr) cat 43- (2.5 Myr) Inter-arm region Mix of young and older star clusters NOTE - Work in progress. All ages still tentative.

Spur/Feather # 2 Spur/Feather # 1

Spur/Feather # 1 Mv < -7 Mv < -6 (less reliable ages) Fairly uniform ages around 100 Myr NOTE - Work in progress. All ages still tentative.

Spur/Feather # 2 Mv < -7 Mv < -6 Gradient with younger clusters near spiral arm