Transcript Document

AY202a
Galaxies & Dynamics
Lecture 21:
Large Scale Motions
Galaxy Evolution
Large Scale Motions
Rubin 1952 Distortions
deVaucouleurs 1956 Local Supergalaxy  Supercluster
Rubin, Ford, Thonnard, Roberts 1976 + answering papers
Peebles – Silk – Gunn early ’70’s Mass and Light
CMB dipole 1976-79 Wilkinson++, Melchiori++ (balloons)
Virgo Infall
Schechter ’80, TD ’80, DH ’82, AHMST ’82
Great Attractor --- 1985 Seven Samurai (BFDDL-BTW)
Kaiser 1985 Caustics
IRAS Surveys 1985  Davis, Strauss, Fisher, H, ++
ORS 1992 Santiago et al.
COBE Dipole ‘97
3.358 mK towards l=264.31 & b= 48.05
Flows and Dipoles
(Silk; Peebles; Gunn)
Gravity
g ~ M/R
Light
2
2
f ~ L/R
So, if <M/L> ~ constant
Gravity Vector
=
Flux Vector
First Target
Virgo
Infall
The Infall S-Curve
Virgo Infall
Schechter 1980 Faber Jackson on 32 E’s
Virgo Infall 190+/-130 km/s
Linear Infall Model for any given galaxy
V0bs = VVirgo x
- w(cos θ –x) [1 – (x2 -2x cosθ +1) –γ/2]
x = distance to galaxy in Virgo Units
Virgo has a density contrast that falls as d-γ
w is the LG infall velocity to Virgo
d is the galaxy’s distance from Virgo
θ is the angular separation between Virgo & the galaxy
Nonlinear Model
(Schechter ’80; Silk ’74, ’77)
Treat each shell around Virgo as its own Universe with its
own average interior density and Hubble Constant and
own present density parameter . Define the
Friedmann arc parameter η
cosh-1(2/ -1) for  < 1
η=
cos-1(2/ -1) for  > 1
& define also the functions
h (η) = sin η (η – sin η)
{
ρ (η) =
(1 cos η)2
(η – sin η)2
(1 – cos η)3
for  > 1
and similar sinh functions for  < 1,
then if ηu is the present universal value of the arc and
ηg is the value for the shell or a particular galaxy g
then the ratios of the local Hubble constant and the
average interior density to the universal H and
average density are given by
h(ηg) / h(ηu) and ρ(ηg) / ρ(ηu)
and VObs = VVirgo
(
hu x – (hu –hl)cosθ – (x – cosθ) (hu – hg)
hg
and the subscript l refers to the Local Group
)
Once ρl/ρu and γ are specified, only ρu
needs to be set to determine all the h’s to also be
specified.
Determining w determines ρu and thus 
w = (hu/hl -1) VVirgo
VVirgo is the Virgo velocity corrected for infall and
any remaining peculiar LG velocity
Accurate Motions
AMHSSB ‘80
Ten Clusters
V0bs = VHubble + VPeculiar + VGrav
we can neglect the gravitational redshifts of galaxies,
then
VPeculiar = VPattern + VRandom
and
VP/VH = -1/3 0.6 (Δ - 0.19Δ2 + …..)
where Δ = δρ/ρ, the overdensity inside

0.6 ~ 3 (
VP
VH
)(
δρ
ρ
)-1 ( 1 + ….)
IR Tully-Fisher
relation
Velocity Perturbations from TF fit to a Virgo Infall Model
z residuals, no infall
AHMST
V infall ~ 250 km/s w.r.t. Hubble Flow
1982
The Great Attractor
Seven Samurai – Lynden-Bell, Faber, Davies,
Dressler, Burstein, Terlevich & Wegner
Faber-Jackson
Dn-σ on 400 E’s
found 570 +/- 60 km/s
towards Centaurus
Han & Mould ’90 Bi Flow
Problems ---(1) Virgo ≠ CMB
(2) Hydra-Cen ≠ CMB
(3) GA + Virgo ≠ CMB amplitude
(4) Honkin’ Pisces-Perseus on the other side
(5) Where is Convergence?
(6) Biasing
Galaxy Bias
If galaxies don’t trace the mass and the galaxy overdensity
is not the mass overdensity, one can use the simple
linear biasing model
δρ
ρ
1 δn
=
b
n
So usually the results of flow field analyses are quoted
in terms of f()  0.6 / b
The Hunt
for the
Dipole
ORS
(Santiago et al.
including Marc)
What is the ideal All-Sky Survey?
Go to the near IR!
---- Beat extinction, the bane
of optical surveys
--- Select for the stars that
trace the baryonic mass
(not star formation)
2MASS Telescope at FLWO
CTIO 1.5-meter
6dF Fiber Positioner, SRC Schmidt, Coonabarabran
•
•
•
Magenta
V < 1000 km/s
Blue
1000 < V < 2000 km/s
Green
2000 < V < 3000 km/s
Red 3000 < v < 4000
Blue 4000< v < 5000
Green 5000 < v < 6000
Red 6000 < v < 7000
Blue 7000 < v < 8000
Green 8000 < v < 9000
Great Wall
LSC
We are here
Pisces-Perseus
KS < 11.25
2MRS Dipole
blue tri = FW - M81, Maffei’s & friends
(Erdogdu et al 2006)
red tri = FW - only LG
Density vs Flow Fields
Don’t do this!
Much Better!
CMB versus LG Reference Frames
Remember,
This Is A
Sphere!
Hectospec Positioner on MMT
300 Fibers
covering a
1 degree field
of view
D. Fabricant
Large
Synoptic
Survey
Telescope
8.4-m
7 degree FOV
Galaxy Evolution
Galaxies Evolve!
A. Population Evolution (Stars)
B. Gaseous Evolution
A + B = Chemical Evolution
C. Dynamical Evolution
There is strong evidence for all three
A – we see galaxies with both young and old stellar
populations and with current star formation\
B – we see infall (e.g. MW high velocity clouds) and
outflow (M33) and cooling flows
A+B we see correlations between stellar age and
stellar [Fe/H] in the MW. Abundance gradients 
in other spirals
C – we see mergers, cannibalism, interactions,
dynamical friction
Basically L, D, U-B, B-V, … L(r,θ), F(λ), Φ(L) all
change with time.
Population Evolution
Tinsley ‘68, SSB ’73, JPH ’77
and the death of the Hubble/Sandage cosmology
program …
The Flux from a galaxy at time t and in band i is
n-1
(n-j)Δt
FG(i,t) =   [ Ψ(k,j) ∫
j
k
(n-j-1)Δt
FK(i,t’) dt’ ]
where FK(i,t’) is the flux of star of type k in
bandpass i at age t’ and ∫ F is the integrated flux in
the jth timestep
This is piecewise, time-weighted summation in an AgeFlux table for stars
Ψ(k,j) is the birth rate function of stars of type k in the
jth time step
Ψ(k,j)  Ψ(m,t) = m–α e–βt
The Initial Mass Function (IMF) is often parameterized as
m–α
with α = 2.35 as the Salpeter slope
The Star Formation Rate (SFR) is often parameterized as
an exponential in time R(t) = A e–βt
or as R(t) = m0/τ e–(t/τ) τ = 1 Bruzual “C” Model
 = 1 - e– (1 Gyr / τ)
Tinsley’s SE models
from Iben ‘66
Tinsley ’68 Just Stars
SED vs
Time
Age
Models
Data
Tinsley Evolution of Broad band Colors
A conundrum in 1973 ….
Gaseous Emission
Continuum flux emitted vs wavelength in volume V is
Fλ = Ne N+ γλ(Te) V ergs s-1 Ǻ-1
Ne & N+ are the electron and ion density and
γλ(Te) is the continuous emission coefficient
Hβ recombination line flux is
FHβ = N(H0) [αHβeff(Te) / αE(Te)] 4.09 x 10 -12 ergs s -1
the numerical factor is the energy of one Hβ photon.
N(H0) is the number of ionizing UV photons from stars
αHβeff(Te) & αE(Te) are the effective recombination
coefficient for Hβ and the total recombination coefficient
Simplify:
1. Assume complete ionization  Stromgren Spheres from
O+B Stars (Ionization Bounded)
so
αE(Te) Ne N+ V ≈ N(H0)
thus
γ λ(Te)
Fλ =
N(H0)
αE(Te)
2. Case B recombination, so α varys by only 4% over the
range 5000 – 20000 K
3. Gaseous emission goes away as soon as the ionizing
photons go away as
τ REC ~ 1.2 x 105 (Ne)-1 years
Line Emission
Gaseous line + Continuum Emission
Starbursts
a.k.a. Composite galaxes --- its all in a name
How Fast They Change!
A 25 Myr Burst on an
old Spiral ΔL = x2
Hβ as a diagnostic
Bursts
Young
Old α = 0.35
α = 3.35
Spectrum
vs
Type
Kennicutt ‘92
Age
C Model vs time
μ = 0.7 model vs time
Modern tracks from
Maeder & Meynet
(and there are others!)
Predicted Evolution
depends on [Fe/H] and
various assumptions re
opacity, mixing,
reaction rates, etc.
! There is not yet
agreement on these!
B&C = Bruzual & Charlot
GW = Worthey
BBCFN = Bertelli et al.
From Charlot, Worthy &
Bressan ‘96
Comparison to
Observations
Charlot, Worthy &
Bressan ‘96
Population Synthesis Models
Depend on
IMF -- shape, slope , upper & lower mass
limits of integration
SFR -- detailed history
[Fe/H] – affects stellar colors, evolutionary
history
Gas -- Chemistry, density, distribution
Dust
Non-thermal activity – presence of an AGN
“You can get anything you want at Alice’s Restaurant”
A. Guthrie