Dynamically distinct zones of disk of M51: diagnostics with HST/WFC photometry

What shall we do today critical review on the diagrams find CAVEATS find extra data / curves to be plotted find extra figures to be produced how to revise format Outline the section of discussion Polish up the title (^^;

Color-mag. diagmram

CMD of SFR / interarm region

left: O(dark blue) + B(light blue) right: RSG (green) + RGB (red) solid curves: logarithmic spiral (eyeball fit)

RSGs with HII regions

RGB/RSG stars on K-band

RGB/RSG on K (zoomed up)

Counts of red stars (V-I > 0.8) RSG dominates in luminosity in the SFRs regions 1-5 as specified above

Blue(OB), RSG(green), black (HII region), CO(red grayscale)

Is the measurement reliable enough ? Independent measurement is welcome rcorot depends on the identification at r = 6 kpc Objective profile-peak detection / cross-correlation more or less requires eye-inspection. Profile/CC are powerful if profile have a good S/N. By providing ranges of azimuth with higher density, peak positions are conservatively shown with ambiguities, which would not alter our conclusion seriously, a posteriori.

peak definition for star/CO profiles

Ω-θ plot for arm 1(red) /2(blue) peak positions (bar); dots simply indicate midpoint of the bars

Ω-θ diagram with choices of axes which one do you favor ?

Main results: Ωp(r) two distinct zones: boundary: 3.5kpc inner: variable Ωp mid-disk: constant boundary: 3.5kpc m=3 resonance ? stars follows the rotation caveat: tOB consistency with Ωp at 6kpc need to be careful to identify SF sites from HII regions thick curve: Rotation curve thin curve: m=3 (Ω±κ/3) dashed curve: m=2 (Ω±κ/2)

How about the outerdisk? (r > 6kpc) seems that OB stars precede HII regions: is Ωp even slower? OB and HII shows small displacement in the bridge between M51 and N5195 (arm 1); is this part a material arm ?

Topics for discussion: Ωp(r) three distinct zones: inner: decreasing Ωp ( boundary: m = 3 resonance ) mid-disk: constant ( boundary: corotation ) outerdisk: decreasing Ωp (?) How did this situation come to be ? i.e. in which situation a constant Ωp is realized ? i.e. what determines Ωp after all ?

Bright (short-lived) “O” stars with shorter tOB

Vp = Ωp ×r ! Thick curve: rotation curve

d = Vp ×tOB !

background keywords for discussion ? swing amplification ?

Related papers for discussion ? Egusa+ 2009 ApJ 697, 1870 Assumed constant Ωp Foyle+ (2011) ApJ 735, 101 No systematic offset are found among any tracers Louie+ (2013) ApJ 763 94 CO/Hα: the best among the tracers Shetty+ (2007) ApJ 665, 1138 Fabry-Perot Hα velocity map (@res. of 25km/s) Zimmer+ (2004) ApJ 607, 285 TW method, Ωp=40 kms/s/kpc (applied 3 galaxies) Meidt+ (2008) ApJ 688, 224 TW method: decreasing Ωp Henry+ (2003) AJ 126, 2831 M=3 arm

Related papers for discussion ? Dobbs+ (2010) MNRAS 403, 625 No single global Ωp: Simulation of M51/N5195 Wada et al. (2008,2011) Grand+ (2012) MNRAS 421, 1529 Simulation favors decreasing Ωp Sellwood ? Minchev+ (2012) AA 548, 124 Comprehensive study on the model disk D’Onghia+ (2013) ApJ 766, 34 Self-induced spiral arm survive due to strong non-linear effects Guiterrez+ (2011) AJ 141, 113 Catalog of HII regions (HST/ACS) Koda+ ApJ 700 L132 GMC: are some topics important for us?

detection & completeness would be revised…

Discriminating shape χ２ ～ 1, sharpness～0 for stars Objects are mostly stars for our case only if they are not fake