Dwarf Galaxies - ideal Laboratories to study astrophysical Processes

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Dwarf Galaxies - ideal Laboratories to study astrophysical Processes Gerhard Hensler University of Vienna Lecture 1 Lecture "Dwarf Galaxies",, Thursday 11:30 am Content/Presenter 7.3. Organization 14.

1 Dwarf Galaxies - ideal Laboratories to study astrophysical Processes Gerhard Hensler University of Vienna Lecture 1 Lecture "Dwarf Galaxies",, Thursday 11:30 am Content/Presenter 7.3. Organization Introduction Morphology and Classification of DGs, Relations, Cosmology Interstellare Medium in DGs 3.4. High/medium-z DGs Dwarf Irregulars; Star formation in DGs 18./25.4. Easter Break 2.5. Chemical Evolution of DGs 9.5. Starburst DGs, Galactic Winds DGs in the Local Group; Satellite Galaxies dsphs DGs in Galaxy Groups and Clusters: the variety of des Assencion 6.6. Galaxy Transformation: Ram-pressure Stripping, Harassment Tidal Tail Dwarf Galaxies Ultra-Compact DGs, Ultra-Diffuse DGs, Low-Luminosity DGs Chemo-dynamical Evolution of DGs 2 1

2 Dwarf Galaxies - ideal Laboratories to study astrophysical Processes I. Introduction 3 Dwarf Galaxies as ideal Laboratories to study astrophysical Processes Gerhard Hensler University of Vienna Bernhard Baumgartner, Jay Gallagher, Matthias Kuehtreiber, Joachim Koeppen, Lei Liu, Thorsten Lisker and the SMAKCED team, Sylvia Ploeckinger, Simone Recchi, Patrick Steyrleithner, Christian Theis, Eduard Vorobyov, many more 4 2

3 5 The Large Magellanic Clouds a dirr on its passage of the Milky Way: smooth evolution 6 3

Wolf-Lundemark-Melotte WLM Prototype of dirrs Wolf 1909, AN, 183, 187 Melotte 1926, MNRAS, 86, 636

1956, AJ, 61, 97 v helio = - 78 20 km/s Sandage & Tammann 1982 (m-m) AV = 25.

93 (Cepheids) The first stellar system deemed extragalactic wasn t... but rather.

4 Wolf-Lundemark-Melotte WLM Prototype of dirrs Wolf 1909, AN, 183, 187 Melotte 1926, MNRAS, 86, 636 Comparison with Barnard Nebula (NGC 6822) mentioning Lundemark Humason et al. 1956, AJ, 61, 97 v helio = km/s Sandage & Tammann 1982 (m-m) AV = (Red Supergiant) Sandage & Carlson 1985, AJ, 90, 1464 (m-m) AB = (Cepheids) The first stellar system deemed extragalactic wasn t... but rather... M31 NGC6822 L ~ 1 L * L ~ L * Hubble (1925): Cepheids NGC6822 at D = 214 kpc (today: 670 kpc) assumed Gaussian LF... Zwicky (1942): LF increases with decreasing luminosity dwarf galaxies = most numerous stellar systems 8 4

with Regulus = Leo, D ~ 270 kpc 9 First Observations of dsph Galaxies Shapely

5 Faint dsphs pure stellar systems, no gas, metal-poor: Z< Z, faint end of dwarf Es, extremely faint: M v >-8 m, very small: d~few 100pc, close to the MWG Leo I with Regulus = Leo, D ~ 270 kpc 9 First Observations of dsph Galaxies Shapely 1938, Bull. Harvard Obs. 109 Baade & Hubble, 1940, PASP, 51, 40 Baade 1944, ApJ, 100, 137 5

6 Hodge 1971, ARA&A 9, 35 Dwarf Galaxies in the Virgo Cluster Morphological peculiarities: Galactic cores in des Class ds0 Blue Compact Dwarfs (BCDs) Ferguson & Binggeli 1994, A&ARev, 6, 67 6

7 Type Examples: ds0 & de 13 Type Examples: de bc, dsph, de blue 14 7

Type Examples: BCD & dirrs 15 DG Properties low mass : 10 6 10 10 M slow rotators : 10 100 km s -1 low luminosity : 10 6 10 10 L low surface

8 Type Examples: BCD & dirrs 15 DG Properties low mass : M slow rotators : km s -1 low luminosity : L low surface brightness (faint end) high surface brightness (BCDGs) low metallicity : 1/3 1/50 Z gas-poor (de s, dsph s) gas-rich (all others) numerous DM dominated (?) 16 8

Dwarf Galaxies Morphology Elliptical Irregular Blue Compact surface brightness increases.

$.. 1/3 des Star formation past continuous starburst fraction 4 :1 5 :1 17 Questions: Are$

9 Dwarf Galaxies Morphology Elliptical Irregular Blue Compact surface brightness increases brightness distribut./colour exponential red patchy blue/ expon. red blue nucleus/ expon. red morphology Ε like ges disk structure bright core gas -- HI (~0.3 M tot ) circumgalactic Z/Z 1/ / /3 des Star formation past continuous starburst fraction 4 :1 5 :1 17 Questions: Are Dwarf Galaxies as simple as they look like? Can one therefore understand their formation and evolution as simply? Do they have the same origin? 18 9

Starbursts + Galactic Wind 19 From low to strong

gas infall are the engines of the galactic wind

10 Starbursts + Galactic Wind 19 From low to strong star formation, forming super-star clusters, numerous SNII explosions drive Galactic Winds In NGC Super Star Clusters at the basis of gas infall are the engines of the galactic wind due to their cumulative supernova II explosions

represent the most common and numerous type of galaxies except in the Field.

11 The Large Magellanic Clouds a dirr on its passage by the Milky Way: smooth evolution in interaction 2/11/17 KASI 21 des dominate in clusters Dwarf elliptical galaxies represent the most common and numerous type of galaxies except in the Field. In the Milky Way neighbourhood the faintest des, called Dwarf Spheroidals dsphs dominate

12 Helmut Jerjen, Mt. Stromlo: 23 The detection of ESO Star formation in the RPS blobs 24 12

13 The Schematic View of DGs Smaller editions of Hubble-type gal.? M, 1-10 kpc, M v >-18 m Sandage & Binggeli (1984) Transformations between morphological types? NGC 205 NGC 4214 M32 Antlia NGC Correlations Ferguson & Binggeli (1994) 26 13

with mass resolution m SPH few x 10 4 few x 10 5 M (Springel et al.

14 Dwarf Galaxies appear in CDM cosmological simulations The zoom-in Aquarius simulations: N-body DM-only make subhalos detectable; with mass resolution m SPH few x 10 4 few x 10 5 M (Springel et al. 2008, MNRAS, 391) 27 The expected distribution of Dwarf Galaxies 28 14

structures but: Downsizing No clear DM content TDGs?

15 DGs as building blocks in the hierarchical CDM scenario Dark Matter substructures form first and assemble to larger structures but: Downsizing No clear DM content TDGs? 29 Star-forming clumps in the tidal tails of the Antenna ( 1992 ) al. Mirabel et 30 15

They are extremely sensitive to 1) their formation epoch, 2) their

16 (2005) ApJ, ca Sternhaufen identifiziert bestehend aus 4 Populationen: jung: 10 Myr 100 Myr 500 Myr alt: 10 Gyr 31 Why are Dwarf Galaxies so interesting? They are extremely sensitive to 1) their formation epoch, 2) their internal evolution, 3) their environmental influence. different formation epochs large variety of evolutionary paths morphological transformations DGs are extremely SS interesting 2019 AP objects 32 16

Dwarf Galaxies as ideal Laboratories to study astrophysical Processes Morphological division of DGs Numerical SF+feedback recipes and parametrizations Low star-formation vs. Starbursts!

17 Dwarf Galaxies as ideal Laboratories to study astrophysical Processes Morphological division of DGs Numerical SF+feedback recipes and parametrizations Low star-formation vs. Starbursts! DG gas evacuation by galactic winds? Transformation channel for dirrs des? Star-formation determinations Starbursts by gas infall des dominate in galaxy clusters: transformation by gas stripping and/or harassment DG formation from merger events? TDGs! DGs as satellites of Hubble-type mature galaxies 33 Dwarf Galaxies and their Formation cosmological: Building Blocks in CDM Cosmology? but: missing Dwarf Satellites and Minihalos, Void problem Faint blue galaxies in the Deep Fields: formation of normal des, dsph; but: Downsizing Re-ionization epoch delayed formation: CNELGs at z : HII Galaxies Transformation: some des in clusters as stripped dirrs? Present-day Formation: Tidal-tail Ds, Ultra-compact Ds Starburst DGs: Gas Infall, transformation by Outflow? Fact: Dwarf Galaxies are easily affected by environmental and internal energetic pocesses 34 Qu s: Transformation? Survival? Formation? diff. DM content? 17

Grebel, 1997 35 How far to observe and how to

18 Grebel, How far to observe and how to detect? Estimate, how far one can observe a DG (from total brightness, surface brihtness, and dimension)! Tolstoy et al. (2010) ARAA,

II. Morphology and Structure of Dwarf Galaxies

II. Morphology and Structure of Dwarf Galaxies Ferguson & Binggeli 1994, A&ARev 6, 67 1 1. Properties low mass : 10 6 10 10 M slow rotators : 10 100 km s -1 low luminosity : 10 6 10 10 L low surface brightness