Scaling Relations of late-type galaxies

Transcription

1 Scaling Relations of late-type galaxies - an observational perspective - Lecture I Lecture II Trends along the Hubble sequence Galaxy rotation curves Lecture III Tully-Fisher relations Marc Verheijen Kapteyn Instituut - Rijksuniversiteit Groningen Bertinoro, May 2006

2 II. Galaxy Rotation Curves observed shapes of rotation curves mass components & RC decompositions disk-halo degeneracy & Maximum Disk hypothesis mass-to-light ratios imprint of luminous matter on RC shape dark matter scaling relations

3 Gas content NGC 2403 optical HI velocity field atomic hydrogen same scale! Fraternali et al, 2001

4 Kinematics - Compact bright galaxy rotation curves Large bright Verheijen, 1997 Broeils, 1992 Intermediate Dwarf Noordermeer, 2006 Casertano & van Gorkom, 1996

5 shapes of rotation curves Compact bright Large bright Dwarf Intermediate Broeils, 1992 Verheijen, 1997

6 shapes of rotation curves Verheijen, 1997

7 slopes of rotation curves rising declining Broeils, 1992

8 Rotation curve decompositions Deriving the distribution of Dark Matter obs stars gas halo V = ( V + V + V )

9 Rotation curves of stars and gas shapes of radial light and HI profiles shapes of the stellar and gas rotation curves spherical bulge + flattened disk calculate potential bulge disk gas thin gas disk Begeman, 1987 mass or mass-to-light ratio M/L of the stars amplitude of the stellar rotation curve mass of gas, corrected for He fraction, is well known

10 Halo mass models Pseudo-isothermal sphere: ρ ρ(r) = o 1+(R/R c ) 2 Hernquist profile: ρ(r) = 2 halo o c 2 R R R c R c V (R) = 4πGρ R [ 1- arctan( ) ] V max halo = R c 4πGρ M o 1 2 V (R) = GM o R halo 2πR o R[1+(R/R )] R + R o 3 max NFW profile: motivated by numerical simulations o V = 1039 M /R halo similar to Hernquist profile at small radius (Navarro, Frenk & White, 1996) o o o o

11 NFW halo model ρ(r) = ρ crit δ c (R/R s)[1+(r/r s)] 2 2 ρ = critical density = 3H /8πG crit halo density R = scale radius = r /c 200 s 3 M = 200ρ (4π/3)r 200 crit 200 δ c = characteristic overdensity = 200 c 3 3 ln(1+c) - c/(1+c) c = concentration index halo rotation curve

12 a severe disk-halo degeneracy maximum disk maximum halo UGC 128 (LSB) - Hernquist halo Halo properties depend on V max disk (M/L)

13 M/L and halo parameters UGC 128 Hernquist halo zero disk Maximum Disk Hypothesis van Albada & Sancisi, M/L R 0 M 0 χ red

14 M/L R c ρ o V (kpc) (M /pc-3 ) ο (km/s) Isothermal sphere Verheijen, 1997 maximum disk Bottema disk M/L=0.6 constrained halo

15 M/L M o R o V max (10 12 M ο ) (kpc) (km/s) maximum disk Bottema disk M/L=0.6 constrained halo Verheijen, Hernquist profile

16 Kinematic effect of stellar disk truncation NGC 3992 Type II

17 HSB-LSB pair Distance (Mpc) i 2 μ (I) (mag/ ) 0 h disk (kpc) M (I) (mag) tot L (I) (L ) tot Ο N2403 U μ (mag/arcsec ) I N2403 U Radius (kpc)

18 HI map XV-diagram HI velocity field M (M ) HI M /L HI M (M ) bar I Ο Ο N2403 U

19 Rotation Curve decompositions Maximum Disk M /L = 1.22 * I M /L = 3.98 * I R c= 5.48 ρ = R c=21.3 ρ = Same Halo M /L = 1.11 * I M /L = 0.73 * I R c= 3.98 ρ = R c= 3.98 ρ =20.7 0

20 three of a kind M μ h o K disk (mag) 2 (mag/ ) (kpc) compact HSB HSB LSB decompositions with identical halos (R =3 kpc, V c halo =149 km/s) (M /L ) * K Galaxies of similar luminosity but different μ and h could have similar halos. o disk

21 Dark Matter scaling relation (?) Assume: M /L = 0.6 * K for all galaxies Verheijen, 1997

22 Calibrating stellar population models Maximum Disk M /L * K Text Salpeter IMF `scaled down Salpeter IMF Bell & de Jong, 2001 photometric M/L are relative, not absolute

23 Disk-Halo degeneracy must be broken! Needed: independent measurement of stellar (M/L) or disk surface density Σ. Obtain M/L via stellar population synthesis models Measure Σ directly via stellar dynamics the Disk Mass Project

24 2 For a sech disk in equilibrium with scale height z : σ = π G Σ z = π G (M/L) μ z z o o o 0 (z = 2h ) z Σ = σ z 2 π G z o or (M/L) = σ z 2 π G μ z o h R / z 0 h z (kpc) Kregel et al de Grijs 1998 Sa Sb Sc Sd h disk (kpc)

25 SparsePak UW - Madison P-Pak AIP - Potsdam 3.5m WIYN, Kitt Peak 71"x72" field of view 82 fibers (4.7" 75 science, 7 sky R (Hα, MgIb, CaII) 3.5m CAHA, Calar Alto 64"x74" field of view 382 fibers (2.7" 331 science, 36 sky, 15 calib. R (MgIb, Hα/Hβ/Hγ)

26 Measuring σz - an example D M K' V max h disk μ0(b) incl ±2 Mpc mag km/s kpc mag/"2 deg 2 μ (mag/" ) NGC 3982 = = = = = = HST/WFPC-2 B-R K I R B Radius (")

27 Measuring σz - an example D M K' V max h disk μ0(b) incl ±2 Mpc mag km/s kpc mag/"2 deg 2 μ (mag/" ) NGC 3982 = = = = = = HST/WFPC-2 B-R K I R B Radius (")

28 UGC 463 UGC 1635

29 N3982 U463 U1635 disk M/L km/s M ο /pc 2 K r/h μ(b) σ z Σ M/L B

30 N3982 U463 U1635 disk M/L km/s M ο /pc 2 K r/h μ(b) σ z Σ M/L B

31 Summary - rotation curves low-mass galaxies show rising rotation curves massive and compact galaxies show declining rotation curves some rotation curves reflect the distribution of luminous matter galaxies with similar baryonic mass live in similar halos HSB galaxies are close to Maximum Disk