What Shapes Galaxies?STScI, 27 April 2016 Anne-Marie Weijmans University of St Andrews Tim de Zeeuw, Eric Emsellem, Davor Krajnović, Pierre-Yves Lablanche & Atlas3D team Intrinsic Shapes of Galaxies

Intrinsic shapes of galaxies X Y

Intrinsic shapes We want 3D shapes from 2D projections We want 3D shapes from 2D projections Modelling galaxies individually is time consuming Modelling galaxies individually is time consuming Statistical approach: recover underlying shape distribution for galaxy population Statistical approach: recover underlying shape distribution for galaxy population –Hubble 1926; Sandage et al. 1970; Lambas et al. 1992; Ryden 2004; 2006; Padilla & Strauss 2008, Méndez- Abreu et al. 2010; Sánchez-Janssen et al. 2016; etc. etc. Combine photometric and kinematic data Combine photometric and kinematic data –use integral-field spectroscopy

Shape depends on viewing angles oblate galaxy triaxial galaxy

Shape depends on viewing angles oblate galaxy triaxial galaxy

Shape depends on viewing angles oblate galaxy triaxial galaxy

Shape depends on viewing angles oblate galaxy triaxial galaxy

Shape depends on viewing angles oblate galaxy triaxial galaxy

Invert observed distribution Assume axisymmetry Assume axisymmetry –p = 1 (oblate galaxies) –q denotes flattening Assume random viewing angles (θ,φ ) Assume random viewing angles (θ,φ ) –integrate over sphere of viewing angles –obtain probability function P(  | q) Invert F(  ) into intrinsic distribution f(q) Invert F(  ) into intrinsic distribution f(q)

The sample Volume-limited parent sample of galaxies Volume-limited parent sample of galaxies –M K < –D < 42 Mpc –|  – 29| < 35 o –|b| > 15 o Discard galaxies with spiral structure  260 early-types Discard galaxies with spiral structure  260 early-types Cappellari et al. 2011a

Separating fast and slow rotators edge-on view for  =  Emsellem et al Regular Velocity  Low Velocity KDC Non-Regular Velocity

Fast versus Slow Rotators Distinguish fast and slow rotators by eye Distinguish fast and slow rotators by eye More differences between fast and slow More differences between fast and slow –slow rotators more massive (Emsellem et al. 2011) –slow rotators in denser regions (Cappellari et al. 2011b) –slow rotators large KDCs (see also McDermid et al. 2006) –slow rotators more misaligned (Krajnović et al. 2011) Simulations support different formation scenarios for fast and slow rotators (e.g., Jesseit et al. 2009; Bois et al. 2011; Naab et al. 2014) Simulations support different formation scenarios for fast and slow rotators (e.g., Jesseit et al. 2009; Bois et al. 2011; Naab et al. 2014)

Observed shapes of Atlas3D sample fast rotators slow rotators round flat

Intrinsic Shapes of Early-Types fast rotators: q = 0.25 slow rotators: q = 0.63 spirals: q = Lambas et al. 1991, Ryden 2006, Padilla & Strauss 2008 Weijmans et al roundflat

Classifying Galaxies Cappellari et al. 2011b van den Bergh 1976 Laurikainen et al Kormendy & Bender 2012

Kinematic information: misalignment Angle between projected axis and minor axis of galaxy image Angle between projected axis and minor axis of galaxy image Caused by: Caused by: –triaxiality –intrinsic misalignment  Binney 1985, Franx et al. 1991

Intrinsic misalignment Oblate galaxies are aligned Oblate galaxies are aligned –only short-axis tube orbits allowed –intrinsic rotation axis coincides with short axis Triaxial galaxies can be misaligned Triaxial galaxies can be misaligned –short and long axis tube orbits allowed –intrinsic rotation axis anywhere in xz plane –assume: θ int depends on triaxiality

Kinematic misalignment kinematic misalignment Ψ on sphere of viewing angles

Best fit: fast rotators are oblate log (1-p) Weijmans et al. 2014

Model vs Observations Weijmans et al. 2014

What about the slow rotators? Weijmans et al. 2014

Conclusions Kinematics constrain intrinsic galaxy shapes Kinematics constrain intrinsic galaxy shapes –identify kinematic populations –kinematic misalignment constrains triaxiality Fast rotators are flatter than slow rotators Fast rotators are flatter than slow rotators –fast rotators have similar flattening as spirals –tail in distribution towards rounder shapes –consistent with oblate population Slow rotators are mildly triaxial Slow rotators are mildly triaxial –larger samples needed!!!

Take-Away Message Fast Rotators Slow Rotators

Velocity structures Regular and non-regular velocity fields (RV and NRV) –a = NRV, low velocity (7)- d = 2  feature (11) –b = NRV, no features (12)- e = RV, no features, double –c = KDC (including CRC) (19) maxima, kinematic twist (209) Krajnović et al a b c c d eee

Fast rotators: disc-like structures Fast rotators show range of D/T Fast rotators show range of D/T –64% of fast rotators have disc-like component –41% of stellar mass in early-types is in discs Krajnović et al Bulge-disc decomposition for 180 non-barred galaxies

Metallicity enhanced discs All SAURON fast-rotators show flattened components with high metallicity All SAURON fast-rotators show flattened components with high metallicity Kuntschner et al. 2010

Intrinsic Shapes of Early-Types Fast rotators are flatter than fast rotators Fast rotators are flatter than fast rotators –overlap towards rounder shapes Fast rotators have similar flattening as spirals Fast rotators have similar flattening as spirals roundflat

Slow rotators not very triaxial Weijmans et al. 2014