DGs Dwarf Galaxies as ideal Laboratories to study astrophysical Processes (a madley of research) Gerhard Hensler University of Vienna Simone Recchi, Sylvia Ploeckinger, Lei Liu, Matthias Kuehtreiber, Patrick Steyrleithner, Bernhard Baumschlager, Thorsten Lisker 10/21/2018 and the SMAKCEDAmity team 6 Dwarf Galaxies as ideal Laboratories to study astrophysical Processes Morphological division of DGs DG gas evacuation by galactic winds; Starbursts? Transformation channel for dIrrs dEs? Starbursts by gas infall dEs dominate in galaxy clusters: transformation by gas stripping Self-regulated star formation at low rates DG formation from merger events? Tidal DGs! 10/21/2018 Amity 7 1 DGs The Schematic View of DGs Smaller editions of Hubble-type galaxies? 6 10 10 -10 M, m 1-10 kpc, Mv>-18 Transformation paths from one morphological Sandage & Binggeli (1984) type to the other are proposed. NGC 205 NGC 4214 M32 Antlia NGC 4449 10/21/2018 Amity 8 Correlations of different galaxy types All “normal“ DGs, dEs and dIrrs follow the same relations even to their faintest end, but differ from UCDs+GCs and from the Hubble- type galaxies. 10/21/2018 Amity 9 Tolstoy et al. (2010) ARAA, 47 2 DGs Questions: Are Dwarf Galaxies as simple as they look like? Can one therefore understand their formation and evolution as simply? Did they have the same origin? 10/ 21/2018 Amity 10 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 DGs10/21/2018 are extremely Amityinteresting AP objects11 3 DGs 10/21/2018 Amity 12 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 10/21/2018 Amity • TDGs? 14 4 DGs Arp 188, the Tadpole Galaxy: bright knots as DG precursors? bright star-formation knots are structured10/21/2018 within the tail. Amity 16 The Large Magellanic Clouds – a dIrr on its passage of the Milky Way: smooth evolution in interaction 10/21/2018 Amity 17 5 DGs Starbursts + Galactic Wind Possible dIrr → dE transformation 10/21/2018 Amity 18 Possibility of dIrr dE transition DGs can show very active modes of star formation, which can be triggered by environmental effects like e.g. gas infall or mergers. Starburst can drive galactic winds! Can these winds evacuate dIrrs from their gas, i.e. transform them to dEs? Understanding the cause of enhanced SF and the impact of massive stars on their environment is of fundamental relevance for understanding the SF process, galaxy evolution also in the Early Universe. 10/21/2018 Amity 19 6 DGs Dwarf Galaxies are strongly affected by Galactic Winds In NGC 1569 2 Super Star Clusters at the base of the gas stream are the engines of the galactic wind due to their cumulative 10/21/2018 supernovaAmity II explosions. 20 Model: • bipolar outflow; • the S part towards observer is unobscured; disk inclination known • metal-enhanced wind: 1-2 Z! X-ray in colors according to hardness (blue: hard, red: soft) overlaid with HI contours (white) 10/21/2018 Amity Martin et al. (2002) 21 7 DGs The mass loss can be determined from the effective yield yeff of the HI ISM. The loss of metals should be visible in the hot gas outflow. Mass loading of super- bubbles diminishs their energetics (thermal+kinetic). 10/21/2018 Amity Martin et al. (2002)22 ApJ, 574 Metal loss through galactic outflows! Garnett (2002) Effective yields yeff of dIrrs < solar! Outflow of SNII gas reduces e.g. O. but: simple outflow models cannot account for gas mixing + turb. heating10/21/2018 Amity 23 8 DGs Galactic winds in Dwarf Galaxies? Continuous mechanical L over 50 Myrs for various galaxy masses Mg and gas densities n: at t=50 Myrs No consistent star formation! 10/21/2018 Amity 24 MacLow & Ferrara (1999) t=100 Myrs 10/21/2018 Amity MacLow25 & Ferrara (1999) 9 DGs Galactic winds in DGs and the fate of metals Luminosity (1038 erg s-1) 0,1 1 10 106 0,18 1 1 1 0,99 1 7 ) 10 3.5e-3 8.4e-3 4.8e-2 M 1 1 1 8 Mass ( 10 1.1e-4 3.4e-4 1.3e-3 0,8 1 1 Mass ejection efficiencies Metal ejection efficiencies 10/21/2018 Amity 27 MacLow & Ferrara (1999) Can strong Galactic Winds solve the CDM cusp/core problem? Loss of low-ang.mom. gas! (2010) Nature, 463 (2012) MNRAS, 422 NO 10solution/21/2018 when metal. mismatchAmity ! 28 10 DGs Testing galactic winds Starburst DGs and BCDGs remain gas-rich and are in different gas disks not exploding, but show perturbed gas dynamics. Observed gas ouflows below escape velocities 10/21/2018 Amity 29 Recchi & Hensler (2013) A&A, 551 Testing galactic winds in different gas disks Initial conditions: 7 8 9 • Baryonic mass: Mb = 10 , 10 , 10 M • Stellar disk by Myamoto-Nagai potential • Isothermal gas disk with flattening b/a = 0.2, 1.0, 5.0 • Gas fraction: 60% (L), 90% (H) • Spherical DM halo with MDM = 10 Mb • SFR~2 10/21/2018 Amity 30 11 DGs Testing galactic winds in different gas disks (2013) A&A, 551 SN ~ 5% Blow-away of total gas almost impossible: Only in lowest-mass DGs and flat, light gas disks, but then all metals are lost. Gas disk, mixing, turbulence, external halo gas,10 /and21/2018 embedded clouds hamperAmity outflow . 31 Testing galactic winds in different gas disks Oxygen ejection: Only lowest-mass DGs with lower gas fraction lose large O fractions. Thick gas disk and massive DGs retain their supernova elements. Recchi & Hensler (2013) A&A, 551 10/21/2018 Amity 32 12 DGs Numerical Simulations of DG evolution Star-formation self-regulationby Stellar feedback M = 1.4 x108 M ; M = 0 M = 2 x109 M ; M = 0 gas,i s,i gas,i s,i 8 9 MDM = 8.4 x10 M MDM = 9.4 x10 M vrot = 30 km/s vrot = ~50 km/s SF as in Köppen, Theis, G.H. (1998, AA, 331) n 4 (c,Tc ) Cnc exp{Tc 10 K} AMR code FLASH Steyrleithner et al. (2017) SPH code Kuehtreiber et al. (2017) Low star-formation rate; No galactic wind! SF concentrated to the central part; Structures form; giant gas holes 10/21/2018 Amity 35 Star formation is self-regulated! What triggers Starbursts? 13 DGs NGC 1569 Gas Infall confirmed! see Muehle et al. (2005) H HI Stil & Isreal (2002) 10/21/2018 Amity 37 Gas infall triggers Starburst The case od NGC 1569: 6 • HI clouds (each ~10 M) fall towards in from a disk • 2 huge super star clusters are formed. (2005, AJ, 130) 10/21/2018 Amity 38 14 DGs NGC 4449 a triggered starburst 10/21/2018 Amity 39 (Hunter et al. 1995) 10/21/2018 Amity 40 II Zw 40 (van Zee et al. 1997) 15 DGs I Zw 18 - a “Youthful-looking Galaxy May Be an Adult” perturbed dIrr with gas infall? (Östlin10/ 21&/ 2018Kunth 2000) Amity 41 (van Zee et al. 1997) But: super star cluster is NGC 1705 not formed in the center !! • Single SSC formed: 5 age 10 Myrs, Mvir 10 M 8 • SSC embedded in HI disk: MHI 10 M • X-ray maxima surrounded by H loops, representing tips of a superbubble, expanding vertically to the HI disk, but confined X-ray contours H overlaid on HI H 10/21/2018 (HenslerAmity et al. 1998) 2 kpc 43 Meurer et al. (1998) 16 DGs 10/21/2018 Amity 44 How are dwarf elliptical galaxies formed? dIrrs do not lose their gas completely by galactic winds! Are all dEs formed morphologically separately? How much environmental effects? How would dIrrs without gas look like? 17 DGs dE Galaxies dominate in clusters Sandage et al. (1984) Binggeli et al. (1987) 10/21/2018 Amity 46 X-ray Gas in Galaxy Clusters 7 TIGM 10 K -4 ... -3 -3 nIGM 10 cm ZIGM 0.2 ... 0.4 Z The Virgo Cluster, a merging complex 10/21/2018 Amity 47 18 DGs 10/21/2018 Amity 48 The vol. density of dIrrs fraction in clusters is the same as in the field. dEs dominate the morphology in clusters! What makes dIrrs dEs? Which process drives gas loss? 1. Galactic winds, gas expulsion 2. Tidal stripping 3. Ram-pressure stripping 10/21/2018 Amity 49 19 DGs dEs in Virgo show a variety of shapes + properties that seem10/ 21to/2018 correlate with the Amity 50 radial cluster distribution. How to distinguish between cluster-born dEs vs. fallen-in, ram-pressure stripped, and harassed former dIrrs? Infalling field dEs not to be discussed! 10/21/2018 Amity 51 20 DGs Distribution of Virgo dE ages (all dEs; Hielscher, Janz et al.), with X-ray contours overplotted. red=older, slower blue=younger, faster dEs as products of infalling RPS dIrrs are expected to • be at higher ICM densities • be at large cluster-centric distances, • to be flatter, • to have smaller Z, • move faster, eccentr. orbits 10/21/2018 Amity 52 Lisker, Janz, Hensler, et al. (2009) ApJ, 706 Dwarf Galaxies are expected to lose gas at cluster infall already by the low-density ICM ram pressure How much gas loss? Ram-pressure effects on star formation: In the DG body? In the RPS gas tail? 10/21/2018 Amity 53 21 DGs Star formation in the RPS blobs The detection of -4 -3 with rates of ~ 10 … 10 M/yr ESO 137-001 10/21/2018 Amity 54 The case of VCC1217 Transformation by RPS RGB UV,U,B,V Hα-off Hα-on not nec.