Cosmic Collisions

Merging from the Zoo SDSS Search Project

Tom Fay 1/10/08 Collisions Affect Galaxy Evolution

{ Hubble classified galaxies as elliptical, spiral, or barred spiral { ‘Irregulars’ < 1%, ignored (based on ‘local neighborhood’) { Irregulars often show collision evidence { Today, galaxy evolution is thought to hinge on galaxy mergers Hubble Tuning Fork: Ellipticals, Spirals, Barred Spirals

Irregular < 1% (M82)

“Early” “Late” [Source: STSI] Ellipticals and Spirals

{ Ellipticals { Spirals z Red z Blue z Little gas (‘dry’) z Have dust and gas z No (‘wet’) z Old, red stars z Star forming z Round/elliptical z Old + new stars z No coherent rotation z Flat disk z ‘Red and Dead’ z Rotating z Some have counter- rotating cores and ‘ripples’ (merger effects?) A Sample From the Galaxy Zoo

{ Following images from Sloan Digital Sky Survey z Quarter of the night sky z Gathered through 5 filters + spectrograph z Limiting magnitude: 22 z 80 million+ galaxies cataloged { Images nominated as ‘best mergers’ on Galaxy Zoo web site. SDSS Sky Coverage Pretty Pairs Dancing Pairs More Complex Pairs

NGC 2820 Odd Pairs

Arp 283 NGC 2799 NGC 2798

Arp 120 More Odd Pairs

Asteroid

NGC 5514 Looks Like…

NGC 6090 How Do They Get That Way???

{ We see a snapshot { Simulations to the rescue! z N-body simulations z Increasing sophistication recently { Check out a few simulation movies… z Mice-like merger: Joshua Barnes z Hi Res Spiral merger: Volker Springel Simulation Timeline

{ 1941: N=74 stars, N-body analog sim (Holmberg) { 1972: early digital sim (Toomres) z N= 120 Stars, merger of equals, unequals; 3-body simulation z Conjecture: Spirals merge into ellipticals z Mergers are ‘short term’ z Mergers form tidal tails & bridges z Mergers cause star formation (gas funneled to core) { Today: N > 1,000,000 z Stars + gas + cold dark matter + bulge + black hole z Many different initial conditions (size, orientation, kind, angle of approach, speed, …)

Juri Toomres, U of Colorado Toomres Model of M51 Toomres Model of Mice Galaxies What Merger Simulations Tell Us

{ Universe Age >> Merger time (~300 million yrs) z Many more mergers than 1% we see locally. z Short time due to dynamical friction of gas halos, tidal tails { Stars + gas + CDM (cold dark matter) needed to produce fast mergers and what we see { Gravitational interactions cause tidal tails, bridges { Star formation triggered by mergers in tails, core { Spirals can merge to form ellipticals { Mergers can form spirals (prograde encounters) { Mergers can form single tails (retrograde encounters) { Mergers can form bars { Mergers can form rings (direct hits) { Minor mergers are slower, form luminous halos What Observations Tell Us

{ Many Ultra Luminous Infrared galaxies show collisional effects { Many Ellipticals show evidence of mergers: shells, even counter-rotating cores { Quasars often in merger remnants { Mergers concentrated in small, compact groups (not larger clusters) { Large ellipticals near center of clusters appear to be mergers (larger, flatter halo) { Populations: 77% spirals, 20% ellipticals, 3% irregulars A Digression: Red Sequence Galaxies

Recent surveys show clear Color vs Magnitude/Mass linear relationship for red galaxies, growing more pronounced since z = 1. Source: Cooper 2006 Red Sequence Mass Growing: How? Maybe mergers…

Source: Cooper 2006 More Images

{ Dispensing with all pretense of scientific explanation or technical details… Elliptical Mergers in a Cluster

Abell 2670 Many multicore, Large central elliptical Cluster + Merger

Large Central Merging Elliptical Merging Ellipticals

NGC 3545 A/B

Spiral Forming or Destroying? Wind-ups

NGC 5541

Arp 239 NGC 5278 NGC 5279

NGC 6050 Ring-forming Collisions

Arp 148 Looks Like…2

NGC 2623 NGC 3561 Arp 105 Pretty Mergers

Arp 301 NGC 5258 (L) 5257 (R)

NGC 5421 Arp 111 Birds

NGC 4837

NGC 2936 Arp 142 Late Stage Mergers or Irregulars?

NGC 3780

NGC 4088 Blue Star-forming Mergers

VV126 Violent Merger, Lovely Sight

Arp 299 NGC 3690

VV059 Multi-mergers

NGC 6027 (Seyfert’s Sextet) Arp 214 Multi-Mergers 2 Blues

NGC 5256

VV360 NGC 4490 Unequal Pairs

Arp 107

NGC 5996 Spiral + Elliptical

NGC 3227 Arp 094

M51 A Tale of Tails

NGC 4676 MRK 0273 (mice) (Partner?)

NGC 5765 Triple Late-stage Merger?

NGC 0660 References

{ Galaxy Zoo z http://www.galaxyzoo.org/Default.aspx { GalCrash collision simulator applet + backgrounder z http://burro.astr.cwru.edu/JavaLab/GalCrashWeb/ z SDSS galaxy study guide z http://cas.sdss.org/dr3/en/proj/basic/galaxies/ { Joshua Barnes Simulations z http://ifa.hawaii.edu/~barnes/transform.html { Galaxy Formation Group z http://www.mpa-garching.mpg.de/galform/ { Galaxy Merger article (1999) for laymen z http://nedwww.ipac.caltech.edu/level5/Struck/frames.html { Galaxy Collision slide set (with sim movies) z http://www.etsu.edu/physics/bsmith/collision s/collisions.html Acknowledgement for SDSS images

Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/.

The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. Toomres: Galaxy Collision Variables