The Baryonic Tully-Fisher Relation

Transcription

1 NRAO - TF35: Global Properties of HI in Galaxies Workshop - 1 April 2012 The Baryonic Tully-Fisher Relation Stacy McGaugh University of Maryland

2 Tully & Fisher (1977) Abs. Mag. line-width

3 9/30/10

4 3/30/10

5 Tully & Fisher (1977) TF great for distances, which are an essential step towards physical understanding: what does it mean? Abs. Mag. line-width The Tully-Fisher Relation is God! Sancisi (1995, private communication)

6 What we measure Luminosity Stellar Mass Gas: HI, H2 Rotation speed line-width rotation curve inclination NGC 6946 Rotation curve data from Boomsma et al (2008) [HI] Daigle et al (2006) [Ha] Blais-Ouellette et al (2004) [Ha] Mass model built from 2MASS K-band data (SSM) (note tiny bulge - Renzo s rule) Vp Vmax Vflat Vp V2.2

7 outer (~flat) velocity maximum velocity peak velocity THINGS data (Walter et al 2008)

8 Velocity estimators: Vflat THINGS data (Walter et al 2008) W20 W50 Vp W20 W50 Vmax

9 Tully-Fisher relation H-band Luminosity Bothun et al. (1985) Sakai et al. (2001) Luminosity and line-width are presumably proxies for stellar mass and rotation velocity. line-width

10 Stellar Mass Tully-Fisher relation Bothun et al. (1985) Sakai et al. (2001) nominal M*/L (Kroupa IMF) Stellar Mass M = ( M L ) L line-width

11 Stellar Mass Tully-Fisher relation Bothun et al. (1985) Sakai et al. (2001) double M*/L Stellar Mass...but stellar mass is completely dependent on choice of mass-tolight ratio (and degenerate with distance) line-width

12 Stellar Mass Tully-Fisher relation Bothun et al. (1985) Sakai et al. (2001) nominal M*/L Stellar Mass...but stellar mass is completely dependent on choice of mass-tolight ratio (and degenerate with distance) line-width

13 Stellar Mass Tully-Fisher relation Bothun et al. (1985) Sakai et al. (2001) half M*/L Stellar Mass...but stellar mass is completely dependent on choice of mass-tolight ratio (and degenerate with distance) line-width

14 Scatter in TF relation reduced with resolved rotation curves (Verheijen 2001) Stellar Mass TF Stellar Mass Stellar Mass line-width outer (flat) velocity

15 Stellar Mass TF Low mass galaxies tend to fall below extrapolation of linear fit to fast rotators (Matthews, van Driel, & Gallagher 1998; Freeman 1999) M = ( M L ) L Stellar Mass outer (flat) velocity

16 Gas Mass TF Gas mass by itself does NOT produce a good TF relation, at least for fast rotators. M g =1.4M HI Gas Mass outer (flat) velocity

17 Stellar Mass TF M = ( M L ) L Stellar Mass outer (flat) velocity

18 Baryonic TF Adding gas to stellar mass restores a single continuous relation for all rotators. M b = M + M g Baryonic Mass Baryonic mass is the important physical quantity. It doesn t matter whether the mass is in stars or in gas. outer (flat) velocity

19 Baryonic TF Twice Nominal M*/L Now instead of a translation, the slope pivots as we vary M*/L. Baryonic Mass Scatter increases as we diverge from the nominal M*/L. outer (flat) velocity

20 Baryonic TF Nominal M*/L Now instead of a translation, the slope pivots as we vary M*/L. Baryonic Mass Scatter increases as we diverge from the nominal M*/L. outer (flat) velocity

21 Baryonic TF Half Nominal M*/L Now instead of a translation, the slope pivots as we vary M*/L. Baryonic Mass Scatter increases as we diverge from the nominal M*/L. outer (flat) velocity

22 Baryonic TF Quarter Nominal M*/L Now instead of a translation, the slope pivots as we vary M*/L. Baryonic Mass Scatter increases as we diverge from the nominal M*/L. outer (flat) velocity

23 Baryonic TF Zero M*/L Now instead of a translation, the slope pivots as we vary M*/L. Baryonic Mass Scatter increases as we diverge from the nominal M*/L. outer (flat) velocity

24 Low mass galaxies considerably expand range of the TF relation. Gas dominated galaxies can provide absolute calibration of mass scale.

25 Gas dominated galaxies can provide absolute calibration of mass scale. Gas Mass gas dominated star dominated Fraction of error budget due to systematics in M*/L Stellar Mass Baryonic Mass Systematic errors in M*/L no longer dominate the error budget for galaxies with Mg > M*.

26 Gas Rich Galaxy Baryonic Tully-Fisher relation (Stark et al 2009; Trachternach et al 2009; McGaugh 2012)

27 select M g >M try fits with many different combinations of IMF and populations synthesis models M b = A V f x slope x =3.94 ± 0.07 (random) ± 0.08 (systematic) Stark, McGaugh, & Swaters (2009, AJ, 138, 392) Fixing the slope to 4 gives A = 47 ± 6M km 4 s 4

28 select M g >M try fits with many different combinations of IMF and populations synthesis models M b = A V f x slope x =3.94 ± 0.07 (random) ± 0.08 (systematic) Stark, McGaugh, & Swaters (2009, AJ, 138, 392) Fixing the slope to 4 gives A = 47 ± 6M km 4 s 4

29 Intrinsic scatter small - consistent with zero σ M < 0.15 dex (consistent with UMa result of Verheijen 2001)

30 Baryonic Tully-Fisher relation: slope depends on Velocity estimator slope: x = 3.5 slope: x = 4 X McGaugh et al. (2000) Begum et al. (2008) Trachternach et al. (2009) Gurovich et al. (2010) McGaugh (2005) Stark et al. (2009) Begum et al. (2008) Trachternach et al. (2009) gas dominated star dominated line-width outer (flat) velocity

31 Data from Spitzer 3.6μ Luminosity Baryonic Mass outer (flat) velocity outer (flat) velocity

32 Stellar mass-to-light ratios in good accord with population synthesis models Recovers expected slope normalization scatter M AV 4 L = f M g L constrains IMF: ~ Kroupa excludes models with excess TP-AGB contributions

33 But why does it work? V 2 = GM R V 4 MΣ Aaronson et al (1979) Galaxies of different surface brightness should fall on different, parallel TF relations.

34 But why does it work? V 2 = GM R V 4 MΣ Aaronson et al (1979) Galaxies of different surface brightness should fall different, parallel TF relations.x

35 But why does it work? CDM halo mass-velocity relation M b f b M tot V 3 Wrong slope, wrong normalization.

36 But why does it work? CDM halo mass-velocity relation M b f b M tot X V 3 Wrong slope, wrong normalization.

37 But why does it work? CDM+Feedback M b f d f b M tot (f v V ) 3 Can now fit anything. As long as the feedback from star formation is most effective in galaxies that have formed practically no stars. log E =1.2 log ( ) V f 100 km s 1 1 ( ) 2 log 100

38 But why does it work? CDM+Feedback M b f d f b M tot (f v V ) 3 X Can now fit anything. As long as the feedback from star formation is most effective in galaxies that have formed practically no stars. log E =1.2 log ( ) V f 100 km s 1 1 ( ) 2 log 100

39 But why does it work? MOND M b = V 4 a 0 G Imposed by force law. Successfully predicted location of gas rich galaxies, but We hate MOND.

40 But why does it work? MOND M b = V 4 a 0 X G Imposed by force law. Successfully predicted location of gas rich galaxies, but We hate MOND.

41 Baryonic TF Relation Fundamentally a relation between the baryonic mass of a galaxy and its rotation velocity Intrinsic scatter negligibly small Physical basis of the relation remains unclear Tantamount to Natural Law? TF is God! Relation has real physical units if slope has integer value - Appears to be 4 if Vflat is used.

42 Application of Renzo s Rule to the Milky Way See poster