Global Scaling Relations of Spiral Galaxies

Transcription

1 Global Scaling Relations of Spiral Galaxies Aaron A. Dutton Max Planck Institute for Astronomy (MPIA), Heidelberg, Germany IAU 311, Galaxy Masses as constraints to Formation Models, Oxford, July 2014

2 Outline The Stellar Initial Mass Function (Cappellari, Romanowsky, Gerhard, Thomas, McDermid, Vazdekis, Conroy, Yi, Verheijen, Treu, Schechter, Smith, Chabrier, Shetty) Velocity - Mass relations (Cappellari, Romanowsky) Angular Momentum (Fall, Falcon-Barroso, Dekel) Evolution (Ziegler, Kassin, Miller)

3 Why the IMF is important Measuring stellar masses of galaxies - Galaxy formation (in)efficiency - Dark matter density profiles dn / d M M -x UV photons - Measuring galaxy star formation rates - Cosmic re-ionization Chemical evolution of galaxies - Supernova rates - Gas recycling Van Dokkum 2008

4 Main uncertainty: Dark matter halo profile Strong degeneracies between stellar and dark matter in galaxy mass models (van Albada & Sancisi 1986) No robust theoretical prediction for dark halo structure in a ΛCDM universe Option 1) Maximum disk (bulge) - Gives upper limit to stellar mass (only assumes DM is not hollow) Option 2) Use vertical kinematics to measure disk mass - Subtract off gas to get stellar mass (DISK MASS PROJECT - see Verheijen) Option 3) Use galaxies with bulge dominated centers - Dark matter fraction is effectively zero, but only gives bulge stellar mass

5 Upper limits to M/L 0.6 Bell & de Jong 2001 From maximum disk fits of spiral galaxies Salpeter IMF overpredicts M/L in many galaxies 0.15 dex lower M/L (known as diet -Salpeter) Milky Way IMFs are OK log10(m/lk) Salpeter IMF Chabrier IMF Spiral galaxies in Ursa Major: Are they typical? (B-R)

6 Scaling Relations Average galaxies Salpeter IMF too heavy in massive spirals diet -Salpeter OK Milky Way IMFs are OK Dutton et al. 2011b Salpeter IMF diet Salpeter Chabrier IMF

7 Brewer et al Upper limits: Strong Lensing!)(!$#"** Critical Curve Strong lensing:!)**$!'!' '!#' projected total mass with critical curve: Mlens Stellar Pop Synthesis: projected stellar mass within critical curve, assuming an IMF: MSPS f* = MSPS / Mlens '!(#$*(## '!(&$(*'& A physical IMF has f* < 1 ''!(

8 !"#!$%"%& Upper limits: Strong Lensing IMF is lighter than Salpeter in massive spirals IMF can be ~2 x heavier than Salpeter in most massive galaxies!)(!$#"** MSPS / Mlens Brewer et al '!(#$*(## Chabrier MSPS / Mlens '''&$%&!% Salpeter Velocity Dispersion '('($!*!,

9 velocity [km/s] velocity [km/s] The disk (bulge) - halo degeneracy (or you get out what you put in) van Albada & Sancisi 1986 Maximal Disk Cored Halo NGC 2403 Minimal Disk Cuspy Halo Total Dark Gas Stars Dutton et al radius [kpc] radius [kpc]

10 Disk Mass Project - Bershady et al. disk surface density vertical velocity dispersion disk scale height geometric constant Challenges 1. measuring σz is hard 2. can t measure σz and hz simultaneously 3. need dynamically cold disks (i.e., no bulges) Strength: Disk Mass Independent of assumptions about dark matter halo

11 Galaxy Disks are Sub-maximal vertical velocity dispersion Bershady et al disk scale height geometric constant } 1. can t measure simultaneously 2. measuring σz is hard 3. need dynamically cold disks Velocity Luminosity Color

12 Galaxy Disks are Sub-maximal vertical velocity dispersion Bershady et al disk scale height geometric constant } 1. can t measure simultaneously 2. measuring σz is hard 3. need dynamically cold disks Dark Matter > Baryonic Matter Velocity Luminosity Color Are all Spirals dark matter dominated within 2.2 disc scale lengths?

13 What about Bulge-dominated Spirals? kpc kpc kpc 20 kpc kpc Bulge stellar mass consistent with Salpeter IMF Disk mass degenerate with dark halo Probability Strong gravitational lenses with star-forming disks (Dutton et al. 2013a) log(mld / MSPS)

14 Sub-maximal disks and maximal bulges Bershady et al Dutton et al. 2013a Warning: constant stellar M/L gives biased results

15 Velocity - Mass relations Velocity (rotation / dispersion / circular) Depends on baryons and dark matter Mass (Luminosity / stellar mass / baryonic mass) Depends on baryons

16 Velocity - Luminosity Scaling Relations Faber-Jackson (1976) ~1200 citations Tully-Fisher (1977) ~1500 citations Velocity Dispersion EARLY TYPES Linewidth LATE TYPES B-Magnitude B-Magnitude 1976: 25 galaxies 1977: 18 galaxies

17 Velocity - Mass Scaling Relations Dutton, Conroy, van den Bosch, Simard, Mendel, Courteau, Dekel, More, Prada, 2011, MNRAS, 416, 322 Faber-Jackson (1976) > 1000 citations Tully-Fisher (1977) >1200 citations Velocity Dispersion EARLY TYPES SDSS data Rotation Velocity LATE TYPES Stellar Mass Stellar Mass 2011: ~100,000 galaxies 2011: ~1500 galaxies

18 Scaling Relation Mass Models As a function of Mstar we know average - dark halo mass (+ halo concentration) - stellar light profile (bulge, disk) - cold gas mass, and size V 2 total (R) = V2 stars (R) + V2 gas (R) + V2 dark (R) Known Known up to IMF Known Known up to halo response Early-types: R=Re Late-types: R=2.2 Rd ~1.3 Re

19 Fiducial Model: Chabrier IMF + Gnedin et al. (2004) halo contraction Faber-Jackson (1976) Tully-Fisher (1977) log(circular Velocity) GOOD MATCH log(circular Velocity) Vrot is ~20% higher than observed log(stellar Mass) log(stellar Mass) Agrees with Schulz et al Agrees with Dutton et al. (2007)

20 Fiducial Model: Chabrier IMF + Gnedin et al. (2004) halo contraction Future: complete samples galaxies on same plot CALIFA, SAMI, MaNGA log(circular Velocity) Model Almost Universal log(circular Velocity) Observed Late types have lower Vcirc log(stellar Mass) log(stellar Mass)

21 Fiducial Model: Chabrier IMF + Blumenthal et al. (1986) halo contraction Early-types: good match Luminosity Late-types: contraction model over predicts rotation velocities. Trujillo-Gomez et al Circular Velocity

22 Cosmological Hydro-Simulations Circular Velocity Vogelsberger et al Illustris Trujillo-Gomez et al Stellar Mass Models over predict rotation velocities of spiral galaxies Solutions: 1) lower observed stellar mass (IMF) 2) lower predicted Velocities (halo response)

23 Varying stellar mass (IMF) and halo response Contraction NFW Expansion log (M star / M SPS ) Halo Response Model Error bars are 2 sigma: halo masses and V/σ Heavier IMF Chabrier IMF (Milky Way) Lighter IMF For Milky Way IMF late-type haloes do not contract early-type haloes contract

24 Dark halo Expansion is possible in cosmological hydro simulations Mashchenko et al. 2008, Governato et al. 2010, Duffy et al. 2010, Pontzen & Governato 2012, Macciò et al. 2012,... DM slope at 1-2% Rvir MaGICC - Stinson et al core NFW contracted Di Cintio et al log(mstar/mhalo) It would be surprising! if real haloes were NFW

25 The Baryonic Tully Fisher relation Motivation: low mass late-types contain lots of cold gas Baryonic Mass = Mstar + Matomic + Mmolecular Gas Rich log (Mgas / Mstar) Dutton et al. 2011b Gas Poor log(mstar)

26 The Baryonic Tully Fisher relation Baryonic Mass = Mstar + MHI + MH2 Baryonic Mass (McGaugh 2000, Bell & de Jong 2001; Geha et al. 2005; Avila-Reese et al. 2008; Begum et al 2008; Stark et al. 2009; Trachternach et al. 2009; Gurovich et al. 2010; Hall et al. 2011; Catinella et al. 2012,...) McGaugh 2011 HI Linewidth, W20/2 [km/s] Vflat [km/s]

27 The Baryonic Tully Fisher relation Baryonic Mass (McGaugh 2000, Bell & de Jong 2001; Geha et al. 2005; Avila-Reese et al. 2008; Begum et al 2008; Stark et al. 2009; Trachternach et al. 2009; Gurovich et al. 2010; Hall et al. 2011; Catinella et al. 2012,...) Baryonic Mass = Mstar + MHI + MH2 Power-law over 4 decades Small scatter: (McGaugh 2012) - observed 0.25 dex - intrinsic < 0.15 dex - Is it too small for ΛCDM? McGaugh 2011 Linewidth Vflat [km/s]

28 Baryonic Mass Gas Mass / Stellar Mass The Baryonic Tully Fisher relation Observed Intrinsic scatter < 0.15 dex (McGaugh 2012) ΛCDM based model scatter 0.15 dex (Dutton 2012) Vflat [km/s] Vflat [km/s] Not a problem. But an intrinsic BTF scatter < 0.1 dex would be

29 cumulative mass Angular Momentum Disk structure is governed by Angular Momentum Distribution AMD of dark matter haloes described by two parameters: 1. Amount of angular momentum spin parameter log-normal distributions <λ > ~ 0.03, σ log λ ~ 0.5 <µ-1> ~ 0.3, σ log µ-1 ~ 0.4 Bullock et al. (2001) 2. Distribution of angular momentum shape parameter (dashed line) uniform sphere in solid-body rotation specific angular momentum, j=j/m

30 Average Spin Parameter Spin Parameters of Disk Galaxies Disk galaxies have lower specific angular momentum than their host dark matter haloes (AM is not conserved?) Virial Mass Dutton & van den Bosch (2012)

31 Excess of low angular momentum in ΛCDM Exponential disks are not natural in ΛCDM van den Bosch, Burkert, Swaters (2001) LCDM (µ=1.3) Data (stars+hi gas) Specific angular momentum r Vrot(r) Galactic outflows (Maller & Dekel 2002, Dutton 2009, Governato et al. 2010, Brook et al. 2011, 2012) preferentially remove low angular momentum material

32 Evolution of disk galaxy scaling relations

33 Scaling relations of Dark Matter Haloes Δ log R vir (z)(m vir ) Δ log M vir (z)(v vir ) Δ log R vir (z)(v vir ) ΔM vir (z)(v vir ) ~ (1+z) -1.3 ΔR vir (z)(m vir ) ~ (1+z) -0.8 ΔR vir (z)(v vir ) ~ (1+z) -1.3 ΛCDM cosmology (Ω M =0.3, Ω Λ =0.7)

34 Observed Evolution is Weaker Dutton et al. 2011a Keys: non-evolving spin parameter, non evolving Mgal/Mvir Theory: Somerville et al. (2008); Firmani & Avila-Reese (2009) Observation: van der Wel et al. (2014) - CANDELS A consistent picture...

35 Velocity - Mass Evolution Miller et al Benson+12 Dutton+11 since z~1 - weak/no evolution (models and obs agree) before z~1 - strong observed evolution (is this physical?) - model predictions diverge

36 Global Scaling Relations of Spiral Galaxies Star forming disks (in the local universe) are consistent with a universal Milky Way IMF, and sub-maximal disks Bell & de Jong 2001, Dutton et al. 2011b, Bershady et al. 2011, Brewer et al But bulges might have a Salpeter-type IMF Dutton et al. 2013a We don t understand the origin of the Tully-Fisher relation Dutton et al. 2007; 2011b, Trujillo-Gomez et al. 2011, Miller et al Specifc Angular Momentum is not conserved in disk galaxy formation van den Bosch et al. 2001, Dutton & van den Bosch 2012

37 Provocative Questions Sub-maximal disks is the wrong question. Isn t Dark Matter fraction fdm(r) what we really want to know? Are any observable dark matter haloes expected to be unmodified by galaxy formation? (or why do people assume ΛCDM = NFW/Einasto?) Could the Tully-Fisher problems just reflect systematic errors in SPS stellar masses?