The problem: Elliptical and dwarf

Françoise Combes Among all types

Elliptical

Spirals

Dwarfs

2 The early part of the tuning fork Are these systems the most simple?

En n=10(1-b/a)

3 Rotation and elliptical galaxies Historically, ellipticals were thought to be flattened by rotation, like spirals are In 1978, it is realized that it is not the case (Illingworth et al 1978) The kinetic support is an anisotropic velocity dispersion This property comes certainly from their formation by merger

4 Measure of velocities in Ellipticals

It is very difficult to measure the rotation in elliptical galaxies

Stellar spectra (absorption lines) are individually and and intrinsically very broad (> 200km/s)

Due to the high pressure of their hot atmosphere

A deconvolution must be carried out: correlation with templates Template as a function of type and stellar populations

5 Stellar spectra galaxy • Absorption lines

Calcium Triplet

Deconvolution:  [Ang] GS*G = S*  LOSVD

LOSVD LOSVD : “Line Of Sight VlVeloci ty Di strib uti on”

Distrib uti on of vel oci ti es retrieved V [km/s] 6 Rotation of Ellipticals

FllFull cilircles: small mass Empty circles: massive Elliptical galaxies Crosses= Bulges

Davies et al (1983)

Solid curve: relation for objects flattened by rotation and with an isotopic velocity dispersion

(Binney 1978) 7 Observation: Densityyp profiles

1/4 1/4 Light profile of deVaucouleurs in r log(I/Ie)= -3.33 (r/re -1)

-2 Hubble profile I/Io = [r/a+1]

8 Theoryyg: King Profiles

F(E) = 0 E> Eo 2 -151.5 2 F(E) = (2  ) o [exp(E[ exp(Eo-E)/ -1] E < Eo

C=log(rt/ro)

rt =tidal radius

ro= core radius

9 Deformations of light profiles

The different profiles correspond to tidal deformations of elliptical galaxies

T1: isolated galaxies T3: with nearbyneihbighbors

Departure from the de Vaucouleurs profile

KdKormendy 1982

10 Possi bl e sh ape f or sph er oï ds

Oblate Prolate Spheroïds of revolution 2 equal axes

If equal axes are major= Oblate, disk, pancake

If equal axes are minor= Prolate, cigar, rugby ball

Hope to consider in the general case 2 axes as close, even if they are not equal To reduce to quasi spheroids ? 11 Triaxiality of ellipticals Observations show that elliptical galaxies have a triiliaxial shape, rather than sphïdlheroïdal wihith 2 equal axes, like oblate/prolate With triaxiality and a variation of ellipticity with radius,  There exists a rotation of isophotes, or twist

This is not an intrinsic deformation!

12 Isophote twist and variation of ellipticity with radius •A triaxial body seen from a random direction will reveal an isophote twist, except when seen along symmetry axes (i.e. PA changes with radius)

a) b) a) Surfaces of constant density. The outer surface is oblate with x:y:z = 1:1:0.46. The inner surface is triaxial with x:y:z = 1:0.5:0.25. b) Image in projection c) Isophotes in projection c) d) d) Isophotes of central region- notice the isophote twist

 • Variation of ellipticity of isophotes with radius radius 13 Disky or boxy morphology •80% of Ellipticals: isophotes deviate from pure ellipses •These deviations at ~1% can be parametrized by decomposing the isophotoal profiles in Fourier series in azimuth

I() = ao +a+ a2cos2 +a+ a4cos4 ellipse component “a4”

Modification of the Hubble tuning fork 14 Isophotes « box » or « disk »

a4=0 Pure ellipse

“ ” a4<0 box •Formedbd by mergers of spiral galaxies •Massive ellipticals •Have in general •Very little rotation Isophote twists •Triaxial

a4>0 “disk” •Indication of a weak disk •Average size •Rotation more •ellipticals pronounced •Oblate 15 Ellipticals & early type Spirals

Certain galaxies are difficult to classify, between lenticulars and ellipticals. The majority of ellipticals have a stellar disk

16 300 galaxies: ATLAS-3D  = Degree of rotation

= apparent elli p tic ity About 85% of spheroidal galaxies have a slow rotation The objects without or with little rotation are giant ellipticals, essentially in dense environments

Capellari et al 2011 Emsellem et al 2011 17 Emsellem et al 2007 Velocity fields of ellipticals/S0

Emsellem et al 2007 19 Faber-Jackson relation for ellipticals

Virgo cluster

RtltRemote clusters

Field galaxies

Ziegler et al 2005 20 Fundamental plane of ellipticals

Re:radius: radius containing half of Discovered by Djorgovski et al 1987 the light 21 Scaling relations

Linking dark matter, responsible of the kinematics

Vflat for spirals, dispersion  for Ellipticals

4 • Tully-Fisher: Mbaryons ~ v • Faber-Jackson: L ~ 4

• Fundamental plane:

22 Simppylified dynamical eq uilibrium

Hydrostatic equilibrium –dP/dr = G M(r) (r)/r2 (isothermal sphere) Pressure P = (()r) 2 (()r) ~ 1/r2 2 ~ GM(r)/r, i.e. M(r) ~ 2 r

2 4 Luminosity L =  re  L ~  /, si M/L = cste

A simple law is not expected, but a lot of scatter instead According to the surface density 

Does this imply M ~ R2 ?

23 Tracers at large distance • Planetary nebulae PN (bright, 30km/s intrinsical dispersion) • Globular clusters GC ((y)but kinematically different?) • X-rays, hydrostatic equilibrium (groups, clusters)

Globular clusters are more abundant in Es than in spirals GC form in mergers of galaxies

GC are not abundant enough, far from the centre Planetary nebulae, line 5007Å [OIII] They are observed at the end of life of like the Sun, red giant, then white dwarf; Asyypmptotic branch of giants AGB

Multi-object rapid observation BtBut requi res Imagery/S pect roscopy  Imagery contra-dispersed 24 Gal ax y-gala xy le ns ing (GG L )

Measure the correlation between galaxies and the density field

« SSctacking »: supe rpos iti on of N objects

Future large surveys LSST

The dark halos have an isothermal distribution from Re to 150kpc Brimioulle et al 2013 25 Galaxy-Galaxy results z(blue) ~0.35, z(red) ~0.28, M/L ~L0.12, M/L =30-300

L~4 L~4

Brimioulle et al 2013 26 Contra-dispersed imagery (CDI)

Field stars have a continuous trace

The PN are a point shifted according to V Douglas & Taylor 1999

Planetary nebulae=PN

27 NGC 4494, PNS Perturbing star

Velocity field of PNe

Napolitano et al 2009 28 Kinematics of N4494

V Dispersion Stars * PN : o

Modelisation Major axis A lot of V Dispersion unknown

Anisotropies In the ppjrojected velocities

Minor ax is

Napolitano et al 2009 29 Models with or without DM

Fraction of DM from 0 to 40%, at 5 Re Velocity anisotropy

Concentration

Mass

Stars * PN : o Triangle: fast Box slow 30 Dark matter in Ellipticals

Planetary nebulae: Romanowsky et al 2003 No dark matter?? N821, N3379, N4494

….. Visible matter (isotropy) - - - isothermal (isotropy)

31 Velocity anisotropy

  = 1 –     0, 1  circular, isotropic and radial orbits

When galaxies form by mergers, orbits in the outer parts are Radius very radial, which explains the weak velocity dispersion in projection (Dekel et al 2005)

The observation of the velocity profile is rather degenerate and cannot yield the dark matter content without ambiguity 32 Young stars = yelow contours

DM

stars

Comparison with observations N821 (green) , N3379 (violet) N4494 (brown), N4697 (blue)

33 Dwarfs Irr : DDO154 the prototype

Carignan & Beaulieu 1989 Galaxies at low surface core, not cusp brightness are dominated by dark matter There exist halos of mass 10 10 M 

Swaters et al 2009

34 Ratio between HI and DM

Factor 8.2 (10 Hoekstra et al 2001)

Lenticulars Early Type dwarfs Irr

 Strong coupling between baryons and dark matter

Swaters et al35 2009 DM/HI M/L ratio of

M/L stars , and 

DM/HI

Depends on morphological type but not on total luminosity M/L

Swaters et al 2009 36 Spiral structure: dwarf galaxies NGC 2915 (Masset & Bureau 2003) The gas disk is unstable against spiral formation It must beself-graviiitating, not didominated by dkdark matter? Or the dark matter is in the plane

37 Discov er y of dw arf gal axi es At the end of spiral classification, Irr, Im, small masses dwarf irregular (dIrr) have gas, and a disk in rotation dwarf Spheroidal (dSph) ensemble of stars very low Lum, without gas dwarf elliptical (dE) spheroïds of stars, without gas, compact

3 9 Lumi nositi es 10 -10 L Aroud the Milky Way: Large and Small Magellanic Clouds The Catalog DDO (David Dunlap Observatory) is a catalogue of 243 dwarf galaxies (1959-1966) by Sidney van den Bergh. 0.1 galaxy/Mpc3. Dwarfs are more numerous than giants

Dwarfs are in general orbiting around giants Mateo, 1998, ARAA Dwarf galaxies (~40) of the Local Group 38 Classification of dwarf galaxies

Grebel 2013

L < L*/100

39 Sandage & Binggeli (1984, AJ, 89, 919) Dwarf ellipticals: very little DM High surface density in the center, Sometimes bright nucleus, exponential profile NGC205 Some contain a stellar disk (Lisker et al 2006, 2007) Stu dyof 476 dE in Virgo (Sloan) Satellite of Andromeda

Several formation ways Ram pressure in groups Harrassment in clusters

Life-time of these spirals?

Total image After unsharp masking 40 Influence of the environment

dE galaxies with nucleus Relaxed in the cluster

The others, with some remaining star formation have just come in come from galaxies of spiral type

Projected density of galaxies in the cluster 41 The dwarf galaxies are associdiated to giants

Central halo + Satellites

Grebel & Guhathakurta

42 Ultra-compact dwarfs UCD

Could come from dE with nucleus?

But excess of Fe/H

Are more similar to globular clusters

No DM..

L  Francis et al 2012 43 Dwarfs dSpp(ph (spheroïdals)

Fornax Galaxies of low surface brightness The smallest known, and the most dominated by the DM Exponential light profile

Thei r masses ~glbllobular cltlusters 5 M*~ a few 10 M

Velocity dispersion ~10km/s

44 Exampp,ple of Draco, at 71kpc

Contours of stellar density, SDSS Sky image of Draco 40% larger, Odenkirchen et al 2001

bound system in equilibrium, no tidal extension, contrary to previous studies 45 Radial profile and kinematics of Draco Stellar density Draco Models

1) Stars alone tot(()r) = *(()r)

2) Stars + DM: tot(r) = *(r) + DM(()r)

• Estimation *(r) of the stellar distribution

• Giant stars as kinematic tracer

required precision  3 km/s 46 Draco: mass model

For the stars (M/L)* ~2~ 2  Draco is dominatd by DM

Modelisation of Jeans equation

Models with different profiles of DM  M (<10‘) well constrained 47 BCD: Blue Compact Dwarfs Galaxies with starbursts, quite fragmented Blue compact regions Poor in metals,,, Rotation, often rich in gas Galaxies in their forming stage, starburst triggered by the interaction between two galaxies?

48 Size-Mass relation (R1/2) These relations allow to distinguish the formation modes Only dSph are in the continuity of E and dE UCD and GC are formed differently and without DM

49 Graham 2011 Characteristics of dwarfs around the galaxies in the Local Group

L 

50 McConnachie 2012 M/L ratio of dwarfs M/L

Dynamical mass

For r< rh rh radius containing ½ luminosity

The most exotic are the dSph around the Milky Way

L 

51 McConnachie 2012 Faber-Jackson relation

(cluster of galaxies) Analog of Tully-Fisher relation for spirals

Dispersion  instead of Vrot 2 σ ~ M1/2/r1/2 r1/2 = 4Re/3 r1/2 at 3D, Re in projection 2 L1/2 = L/2 = IeπR e .

Tollerud et al 2011 52 3 quantities better seen in 3D

M/L of spheroidal systems M/L ~3, only for dSph and CSph need DM

Tollerud et al 2011 53 Fundamental plane: relations MRL

1441.44 0300.30 • M1/2 ∝ r1/2 ∝ L1/2 For the dwarfs dSph, dIrr.. 1421.42 3203.20 • M1/2 ∝ r1/2 ∝ L1/2 For the giants CSph

Tollerud et al 2011 54 Predictions CDM: ’cusp’ or ’core’

Radial distribution of dark matter density

Power law of the density  ~1-1.5, observations  ~0

Core

55 Dwarf Spp,heroidals, satellites of the MW

More than half of them have been discovered recently, thanks to the SDSS (Sloan Digital Sky Survey, started in 2000)

Always DM 7 10 M  for R < 300pc

56 Strigari et al 2008 Surface density of the dark matter

dSph dIrr LSB Spi Ell

Kormendy & Freeman 2004 Gilmore et al 2007, Donato et al 2009

2 M = 142 M  /pc 57 Scaling Laws, L-

Re: effective radius Containing half of the mass

M/LV= 8 for E, 5 for S0, bulges, 2 for S, dw

Kormendy & Freeman 2014

58 Conclusion: DM in Ellipticals & dwarfs

Difficult to test the total mass, with only the velocity dispersion DjtiDeprojection problem i3Din 3D

Ellipticals and dE: the surface density of stars is high  Very little evidence of dark matter, same for UCD

The dwarf Irregulars are rich in gas -- The rotation curves show that dark matter dominates -- CliCoupling with baryons. Ra tio DM/HI ~ 10 -- Tully-Fisher relation

The dwarf spheroidals: dSph, dominated by DM Very small masses (GC?) and low surface brightness These 2 types of dwarfs show cores and not cusps 59