Bar-driven Spirals? S 4 G perspective Heikki Salo, Univ. Oulu, - PowerPoint PPT Presentation

Bar-driven Spirals? S 4 G perspective Heikki Salo, Univ. Oulu, Finland Dynamics of Disk Galaxies workshop, Seoul 21.10.2013 Thanks to: Eija Laurikainen, Simon Diaz, Martin Herrera, Jarkko Laine, Sebastien Comeron + S 4 G team 1

TOPIC: What is the observational evidence for a connection between bar and spiral structure? Ongoing study using the 3.6 micron data from S 4 G (Spitzer Survey of Stellar Structure in Galaxies, PI K. Sheth) 2

BARS & SPIRALS Different scenarios (see Jerry Sellwood’s review on Tuesday) 1) Spiral = direct extension of bar mode Either in the sense of classical density wave picture or in manifold-theory (Lia Athanassoula on Tuesday) 2) Spiral mode is coupled to bar via resonance coupling 3) Spiral is an independent mode or transient pattern, not connected to the bar Not easy to distinguish these scenarious based on morphology: 1) ⇒ Expect correlation between amplitude of bars and spirals Same pattern speed ⇒ phases also related 2) ⇒ Correlation between amplitudes 3) ⇒ No correlation 3

Observational support for bar/spiral connection? - Pictorial examples easy to find GD-spirals more frequent in barred (Kormendy 1979, D & B Elmegreen 1982) - Statistical near-IR studies: yes, perhaps, no? • Block et al. (2004): sample of 17 galaxies K bar-related torque strength Q b strongly correlated with spiral-related Q s • Buta et. al 2005: 147 galaxies from OSUBGS (H-band, Eskridge 2002) possible weak correlation between Q b and Q s • Buta et al. 2009: deep Ks sample with AAT, 23 galaxies: no correlation • Similar negative results: Durbala et al. 2009 (Sloan i, 46 galaxies ), Seiger et al. 2003 (K band, 41 galaxies) OSUBGS Buta et al. 2005 0.7 0.6 maximum FT/FR (SPIRAL) 0.5 0.4 0.3 0.2 0.1 4 0.0 0.0 0.2 0.4 0.6 0.8 maximum FT/FR (BAR)

Characterization of bar strength: Azimuthal Fourier amplitudes of density (e.g. Elmegreen & Elmegreen 1985) m = ∞ " # X I ( r, φ ) = I 0 ( r ) 1 + A m ( r ) cos [ m ( φ − φ m ( r ))] m =1 Tangential force amplitudes (normalized to axisymmetric force) (Combes and Sanders 1981) F T/F R = max( | F T ( r, φ ) | ) ( ≡ F T/F R in this talk ) < | F R ( r, φ ) | > ⇒ maximum at bar region = Q b NGC 1452 2.2 µ m 100 1.2 0.8 Q b max A 2 1.0 0.6 50 0.8 FT/FR 0 0.6 0.4 A2 bar 0.4 -50 0.2 0.2 -100 0.0 0.0 -100 -50 0 50 100 0 20 40 60 80 100 0 20 40 60 80 100 5 r (arcsec) r (arcsec) /home/heikki/NGC1566_OULU2011.dir/NGC1452_schema_beijing2012 heikki@pc091079 Sun Oct 20 08:42:57 2013

Bar and spiral forcing: Separate non-axisymmetric bar and spiral contributions to density ⇒ A 2 ( bar ) , A 2 ( spiral ) Q b , Q s ngc1566 1.0 R 2s R bar 100 0.5 A2 spirals bar 0.0 0 0 50 100 150 200 0.3 bar spirals -100 0.2 bar+spiral FT/FR 0.1 -200 0.0 -200 -100 0 100 200 0 50 100 150 200 6 r (arcsec)

Calculation of forces with NIRQB -code : (Salo et al. 1999, AJ 117, 792; Laurikainen and Salo 2002 MNRAS 337, 1118) (Applied to to 2MASS, OSUBSGS, NIRSOS, AAT samples in Buta et al. and Laurikainen et al. studies) • Assumed: near-IR light traces Σ (M/L= constant, or a function of radius) vertical scale height h z (e.g. from hr or RK 20 ; several choices for vertical profile exp, sech2, gaussian ...) 2-fold uncertainty in hz ⇒ < 25% uncertainty in Qb • Azimuthal Fourier decomposition at radial zones (typically m=0, 2, 4, 6, 8...) , + polar FFT force integration directly from m -components) NGC936 NIRSOS 2MASS 2MASS: uncleaned azimuthal filtering ⇒ no spurious force peaks in the noisy outer disk = Important advantage over Cartesian integration 0.3 0.3 0.3 CART POLAR: m MAX =8 0.2 0.2 0.2 m MAX =6 F T /F R m MAX =4 m MAX =2 0.1 0.1 0.1 0.0 0.0 0.0 7 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 rad (") rad (") rad (")

Re-analysis of bar-spiral correlation: OSUBSGS and AAT-samples Salo, Laurikainen, Buta, Knapen 2010: - Small samples/selections effects ⇒ explain earlier inconclusive resuts - Stronger correlation when comparing spiral amplitude A 2 ( r ) against the gravity forcing by bar at the same distance, Q bar ( r ) (instead of using the maximum values) Example: Buta et al. (2009) deep AAT-sample: Clear correlation: between local forcing due to bar, if evaluated No correlation: at the location of radial maximum of spiral A2 max of Q bar and max of A 2 (spiral) 1.0 0.5 a) b) R 2 s/R bar <1.5 R 2 s/R bar <1.5 0.8 0.4 R 2 s/R bar >1.5 R 2 s/R bar >1.5 Q bar (R=R 2 s) 0.6 0.3 max Q bar 0.4 0.2 0.2 0.1 8 0.0 0.0 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 max A 2 (spiral) max A 2 (spiral)

For both OSUBSGS and AAT -samples: Statistically significant correlation between local bar forcing and local spiral amplitude up to 1.5 bar lengths (Salo et al. 2010) m > 0 density amplitude set to zero for r > R bar in calculation of forces correlation between local FT/FT and A 2 looked at 4 different distances outside the bar 1.2 1.2 r/R bar = 1.1 r/R bar = 1.3 1.0 1.0 r sample = 0.64 r sample = 0.57 p = 1.3e-11 p = 1.2e-08 0.8 0.8 A 2 (r) A 2 (r) 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 0.0 0.1 0.2 0.3 0.00 0.05 0.10 0.15 Q bar (r) Q bar (r) 1.2 1.2 r/R bar = 1.5 r/R bar = 1.7 1.0 1.0 r sample = 0.30 r sample = 0.074 p = 0.0040 p = 0.26 0.8 0.8 A 2 (r) A 2 (r) 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 9 0.00 0.02 0.04 0.06 0.08 0.00 0.01 0.02 0.03 0.04 Q bar (r) Q bar (r)

Analysis of S4G sample Need: Sky-subtracted, cleaned images Reliable (=visually checked) galaxy orientation parameters (P4) and bar lengths Calculation of Fourier amplitudes and forces Original S4G with 2352 galaxies ⇒ bar force calculated for 532 galaxies removed 374 ’bad’ cases (too small FOV, image defects, bright star, large sky-gradient, ⇒ 1978 galaxies superposed companion, deformed, or with unreliable orientation) limit to i < 65 ◦ ⇒ 1172 galaxies barred (bar length can be estimated) ⇒ 786 galaxies barred + trailing/leading sense of spirals visible ⇒ 729 galaxies force calculations so far for 532 galaxies NGC1097 .SBS3.. uc=0 BARLEN = 96.2" (sky-plane) uc=0 1.2 - max: 95.1" 0.646 min: 120.6" 0.513 1.0 0.8 200 ELLIP Example of bar length measurements: 0.6 0.4 visual bar length, position angle, max ellipticity 100 0.2 0.0 (Martin Herrera / Simon Diaz) 0 50 100 150 200 250 300 a (arcsec) 0 200 dPA -28.2 150 -100 100 PA -200 50 10 0 0 50 100 150 200 250 300 -200 -100 0 100 200 a (arcsec) arcsec /home/heikki/S4G_BARS.dir/barlen_270611_inc65.dir/NGC1097_barlen heikki@hiisi.oulu.fi Mon Jun 27 15:38:21 2011

For S4G-sample: (Salo et al. in preparation) Significant correlation between max Q b ( bar ) and max A 2 ( spiral ) Holds both for strongly (SB) and weakly-barred (SAB) galaxies ALL SB, SAB 1.2 N_SB =261 0.269 p=0.0000 N_SAB=227 0.286 p=0.0000 1.0 0.8 A2(spir) 0.6 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 Qb (bar) 11

The correlation of max Q bar and max spiral A 2 is significant even at ≈ 3 bar radii. 1.5 - 2.0 Rbar 2.5 - 3.0 Rbar 3.0 - 3.5 Rbar ALL SB, SAB ALL SB, SAB ALL SB, SAB 1.2 1.2 1.2 N_SB =282 0.314 p=0.0000 N_SB =279 0.199 p=0.0008 N_SB =264 0.244 p=0.0001 N_SAB=238 0.345 p=0.0000 N_SAB=233 0.246 p=0.0002 N_SAB=223 0.252 p=0.0001 1.0 1.0 1.0 A2(spir) [1.5 < R/Rbar < 2.0] A2(spir) [2.5 < R/Rbar < 3.0] A2(spir) [3.0 < R/Rbar < 3.5] 0.8 0.8 0.8 0.6 0.6 0.6 0.4 0.4 0.4 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 Qb (bar) Qb (bar) Qb (bar) max FT/FR(BAR) vs. A2(R) 0.8 SB 236 SAB 203 rank correlation between Q bar and A 2 ( r ) 0.6 as a function of R/R bar Symbols: correlation significant ( p < 0 . 02 ) rank correlation 0.4 0.2 12 0.0 0 1 2 3 4 R/Rbar

Correlation between local Q bar and local spiral A 2 even stronger near the bar, but drops more rapidly with distance (consistent with salo et al. 2010: local values showed correlation, global not) max FT/FR(BAR) vs. A2(R) local FT/FR(BAR) vs. A2(R) 0.8 0.8 SB 236 SB GLOBAL LOCAL SAB 203 SAB 0.6 0.6 rank correlation rank correlation 0.4 0.4 0.2 0.2 0.0 0.0 0 1 2 3 4 0 1 2 3 4 R/Rbar R/Rbar 13

S4G sample size (at least almost) large enough to allow further division to subsamples: max Q bar and local spiral A 2 for different types: T-interval = -3,-1 T-interval = -1, 1 T-interval = 1, 3.5 1.2 1.2 1.2 N_SB= 19 0.498 N_SB= 42 0.188 N_SB= 37 0.404* N_SAB= 15 0.757* N_SAB= 46 0.329 N_SAB= 48 0.390* 1.0 1.0 1.0 0.8 0.8 0.8 A2_spir A2_spir A2_spir 0.6 0.6 0.6 0.4 0.4 0.4 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 Qb Qb Qb T-interval = 3.5, 6 T-interval = 6, 8 T-interval = 8, 10 1.2 1.2 1.2 N_SB= 22 0.654* N_SB= 76 0.401* N_SB= 90 0.372* N_SAB= 55 0.405* N_SAB= 31 0.263 N_SAB= 44 0.489* 1.0 1.0 1.0 0.8 0.8 0.8 A2_spir A2_spir A2_spir 0.6 0.6 0.6 0.4 0.4 0.4 0.2 0.2 0.2 0.0 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 14 Qb Qb Qb