STELLAR SHELLS IN THE ILLUSTRIS SIMULATION Ana-Roxana Pop in - PowerPoint PPT Presentation

STELLAR SHELLS IN THE ILLUSTRIS SIMULATION Ana-Roxana Pop in collabora*on with Lars Hernquist, Annalisa Pillepich, Nicola Amorisco En*re group Satellite forming shells radial velocity x y radial distance Ana-Roxana Pop Stellar Shells in Illustris Heidelberg - Stellar Halos, July 2018

NS-NS merger - GW170817 A few famous shells occurred in a shell galaxy (NGC 4993) Hubble Credits: NASA, ESA, A. Levan (U. Warwick) NGC 474 CFHT/Coelum/MegaCam J.-C. Cullandre & G.A. Anselmi ESO 381-12 NASA, ESA, P. Goudfrooij (STScI) DECam coadded image Ana-Roxana Pop Ana-Roxana Pop Galaxies with Stellar Shells Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

Tidal Features in Illustris Type I Shells Type II Shells Streams and other ]dal features Pop+2017a, arXiv:1706.06102 INTRODUCTION I. FORMATION II. METALLICITY III. HALO SHAPES Ana-Roxana Pop Galaxies with Stellar Shells Heidelberg - Stellar Halos, July 2018

From Shells to Streams increasing angular momentum of the accreted satellite radial orbit more circular orbit Sanderson & Helmi 2013 SHELLS “wrappings” STREAMS Mar]nez-Delgado+2008 Arp 230 (Arp 1966) Hendel & Johnston 2015 Ana-Roxana Pop Ana-Roxana Pop Ana-Roxana Pop Galaxies with Stellar Shells Galaxies with stellar shells Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018 ITC Luncheon, April 2018

Different Types of Shells Type I shells radial orbit shells aligned with the major axis NGC 7600 - Turnbull et al., 1999 SHELLS Prieur 1988 Type II shells Prieur (1989) and Wilkinson et al. (1987) introduced a system of classifying shells based on their morphology shells more randomly distributed Prieur 1988 NGC 474 - Turnbull et al., 1999 Ana-Roxana Pop Ana-Roxana Pop Ana-Roxana Pop Galaxies with Stellar Shells Galaxies with stellar shells Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018 ITC Luncheon, April 2018

Observed shell galaxy Shell galaxies in the Illustris simula]on Ana-Roxana Pop Ana-Roxana Pop Ana-Roxana Pop Shell Galaxies in Illustris Shell galaxies in Illustris Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018 ITC Luncheon, April 2018

Observed shell galaxy Shell galaxies in the Illustris simula]on PART 1 (arXiv:1706.06102) — First study of shell galaxies in a cosmological se^ng (Illustris) • What is the frac*on of shells in a cosmological simula*on? • How do shells form? PART 2 (arXiv:1708.01615) — Metallicity of stellar shells PART 3 (paper in progress) — The shape of halos hos*ng shell galaxies Ana-Roxana Pop Ana-Roxana Pop Ana-Roxana Pop Shell Galaxies in Illustris Shell galaxies in Illustris Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018 ITC Luncheon, April 2018

Observed shell galaxy Shell galaxies in the Illustris simula]on M 200crit > 6 × 10 12 M � Galaxy sample : 220 most massive galaxies in Illustris at z=0, Two selec]on steps: Step 1 Observer Visual iden]fica]on Score of 2 Score of 1 Score of 0 INTRODUCTION III. HALO SHAPES Ana-Roxana Pop Ana-Roxana Pop Iden*fying Shell Galaxies in Illustris Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

Observed shell galaxy Shell galaxies in the Illustris simula]on M 200crit > 6 × 10 12 M � Galaxy sample : 220 most massive galaxies in Illustris at z=0, Two selec]on steps: Theorist Step 1 Step 2 s) Observer n o i t a Visual iden]fica]on l u (s m i Stellar History Catalogs & tracing the individual satellites forming shells INTRODUCTION II. METALLICITY III. HALO SHAPES Ana-Roxana Pop Ana-Roxana Pop Iden*fying Shell Galaxies in Illustris Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

At each important *me in the Theorist life*me of a star Step 2 (forma]on, accre]on, stripping) s) we save informa*on about the star n o i t a and its progenitor galaxy. l u (s m i Stellar History Catalogs & tracing the individual satellites forming shells En*re group Satellite forming shells radial velocity x y radial distance INTRODUCTION I. FORMATION II. METALLICITY III. HALO SHAPES Ana-Roxana Pop Ana-Roxana Pop Iden*fying Shell Galaxies in Illustris Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

Shell Galaxies in Illustris We find that the frac]on of shell galaxies increases with stellar and virial mass. In our total sample of 220 galaxies, we find 18% +/- 3% of the galaxies have shells. This es]mate is in overall agreement with the latest observa]ons. 18% shells out of 220 galaxies with M 200crit > 6 × 10 12 M � Pop+2017a, arXiv:1706.06102 Ana-Roxana Pop Ana-Roxana Pop Shell Galaxies in Illustris Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

The Progenitors of Shell Galaxies increasing angular momentum of the accreted satellite radial orbit more circular orbit most studies focused on radial minor mergers Sanderson & Helmi 2013 however, there are several observa*ons of shells SHELLS “wrappings” STREAMS that seem to be the result of major mergers : Schiminovich et al. 1995, Balcells et al. 2001 Goudfrooij et al. 2001, Serra et al. 2006 Mar]nez-Delgado+2008 Arp 230 (Arp 1966) Hendel & Johnston 2015 Ana-Roxana Pop Ana-Roxana Pop Ana-Roxana Pop Galaxies with Stellar Shells Galaxies with stellar shells Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018 ITC Luncheon, April 2018

The Progenitors of Shell Galaxies We aim to iden*fy the We aim to iden*fy the key key parameters that parameters that make a make a satellite likely satellite likely to form shells to form shells in a in a cosmological segng ! cosmological segng. Order-zero recipe: 1. radial infall orbit 2. massive satellite the satellites forming shells are rela*vely massive p<0.0001 3. accre*on *me 4-8 Gyr ago compared to the host galaxy! Ana-Roxana Pop Forma*on of Shell Galaxies Heidelberg - Stellar Halos, July 2018 PART I - Selec*ng Shell Galaxies in Illustris PART II - Global Proper*es of Shell Galaxies PART III - Shell Progenitors and Their Mergers

The Progenitors of Shell Galaxies We aim to iden*fy the We aim to iden*fy the key key parameters that parameters that make a make a satellite likely satellite likely to form shells to form shells in a in a cosmological segng ! cosmological segng. Order-zero recipe: 1. radial infall orbit 2. massive satellite p<0.0001 3. accre*on *me 4-8 Gyr ago Order-zero recipe: 1. radial infall orbit 2. massive satellite 3. accre*on *me 4-8 Gyr ago Radial Velocity Ratio (@ t_acc) Ana-Roxana Pop Forma*on of Shell Galaxies Heidelberg - Stellar Halos, July 2018 PART I - Selec*ng Shell Galaxies in Illustris PART II - Global Proper*es of Shell Galaxies PART III - Shell Progenitors and Their Mergers

What type of mergers produce shell galaxies? Radial Velocity Ra*o at Accre]on Time Pop+2017a, arXiv:1706.06102 INTRODUCTION I. FORMATION II. METALLICITY III. HALO SHAPES Ana-Roxana Pop Forma*on of Shell Galaxies Heidelberg - Stellar Halos, July 2018

What type of mergers produce shell galaxies? Small Satellite Small satellites (stellar mass ra]os ~1:10) can produce shells Central Host if they arrive on radial orbits Radial Velocity Ratio (@ t_acc) R 200mean Stellar Mass Ratio Pop+2017a, arXiv:1706.06102 Ana-Roxana Pop Ana-Roxana Pop Forma*on of Shell Galaxies Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

What type of mergers produce shell galaxies? Small Satellite Small satellites (stellar mass ra]os ~1:10) can produce shells Central Host if they arrive on radial orbits Radial Velocity Ratio (@ t_acc) R 200mean Massive Satellite Very massive satellites (stellar mass ra]os > 1:3) have their final infall orbits Central radialized by dynamical Host fric]on. R 200mean Stellar Mass Ratio Pop+2017a, arXiv:1706.06102 Ana-Roxana Pop Ana-Roxana Pop Forma*on of Shell Galaxies Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

What type of mergers produce shell galaxies? Remember Nicola “the younger” talk on Monday! Radial Velocity Ratio (@ t_acc) Msat/Mhost - 1/6 Amorisco 2017a higher mass ra]o (close to major mergers) Stellar Mass Ratio more efficient orbit radializa]on Msat/Mhost - 1/40 Pop+2017a, arXiv:1706.06102 Ana-Roxana Pop Ana-Roxana Pop Forma*on of Shell Galaxies Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

Metallici]es of Stellar Shells Stellar shells formed due to rela*vely major mergers can be more metal rich than host stars at similar radii . Pop et al. 2018, in prepara]on Pop+2017b, arXiv:1708.01615 Ana-Roxana Pop Ana-Roxana Pop Metallici*es of Stellar Shells Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

Metallici]es of Stellar Shells Pop et al. 2018, in prepara]on Pop+2017b, arXiv:1708.01615 Ana-Roxana Pop Ana-Roxana Pop Metallici*es of Stellar Shells Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018

Metallici]es of Stellar Shells See Erin’s talk on observed HSC shells arXiv:1805.05970 Pop et al. 2018, in prepara]on Pop+2017b, arXiv:1708.01615 Ana-Roxana Pop Ana-Roxana Pop Metallici*es of Stellar Shells Heidelberg - Stellar Halos, July 2018 ITC Luncheon, April 2018