Breathing in, I calm myself This is a wonderful moment Breathing out, I smile Living in the present moment --Thick Nhat Hanh

SOAR 2014: Galaxies Aileen A. O’Donoghue Priest Associate Professor of Physics

Galaxies  9/9/14  Milky Way Galaxy Contents & Motions  9/16/14  Milky Way Environment & the Local Group  9/23/14  Other Galaxies & Clusters of Galaxies  9/30/14  Expansion, History & Evolution of the Universe  9/9/14  Milky Way Galaxy Contents & Motions  9/16/14  Milky Way Environment & the Local Group  9/23/14  Other Galaxies & Clusters of Galaxies  9/30/14  Expansion, History & Evolution of the Universe

SOAR: Galaxies The Milky Way Environment & the Local Group Aileen A. O’Donoghue Priest Associate Professor of Physics

The Local Group  The Milky Way’s Galaxy Cluster > 54 galaxies within 5 million light years Andromeda (M31) & Satellites M32 & M33 Triangulum (M110) Milky Way

The ‘Hood

Milky Way’s Environment  IntraCluster Medium (ICM)  Did galaxies form from this gas?  IntraCluster Medium (ICM)  Did galaxies form from this gas?

Milky Way’s Environment  Galaxies emit and absorb gas

Milky Way’s Environment  Milky Way’s Lumpy Halo  Stars, Globular Clusters, Gas, Dwarf Galaxies  Milky Way’s Lumpy Halo  Stars, Globular Clusters, Gas, Dwarf Galaxies Being studied by RA dial V elocity E xperiment by Institutions from 11 nations

Galactic Cannibalism  Galaxies grow by eating their neighbors  MW has 9 dwarf companion galaxies  Halo stars from disrupted dwarfs  Galaxies grow by eating their neighbors  MW has 9 dwarf companion galaxies  Halo stars from disrupted dwarfs

The Milky Way Growing?  Galaxies merge with other galaxies “Galactic Cannibalism”  Milky Way has two known merging galaxies  Dwarf Elliptical Galaxy in Sagittarius  Dwarf Galaxy in Canis Minor  Closest galaxy in process of merging  Researchers expect to find more!  Galaxies merge with other galaxies “Galactic Cannibalism”  Milky Way has two known merging galaxies  Dwarf Elliptical Galaxy in Sagittarius  Dwarf Galaxy in Canis Minor  Closest galaxy in process of merging  Researchers expect to find more!

Sagittarius Dwarf Elliptical  Part of the “Sagittarius Stream” of gas & stars  52 klyc from galactic center  Has passed through MW 10 times  Dark Matter indicted by lack of disrupton!  Part of the “Sagittarius Stream” of gas & stars  52 klyc from galactic center  Has passed through MW 10 times  Dark Matter indicted by lack of disrupton! Stars of SgrDEG have different speeds than MW stars SgrDEG on far side of galactic center

Sagittarius Stream  Stars & gas stripped from SgrDEG “Flyaround” of Milky Way with Sagittarius Stream APODAPOD image of Sagittarius Stream

Sagittarius Stream  Simulations of tidal stripping of SgrDEG ~ 2 billion BCE to 500 million CE  Simulations of tidal stripping of SgrDEG ~ 2 billion BCE to 500 million CE Color indicates time of tidal stripping Color indicates stellar density Simulations by Kathryn V. Johnston, Wesleyan UniversityKathryn V. Johnston

Canis Minor Dwarf  Discovered in 2003, 25 kly from MW center

CMi Dwarf  Discovered in 2003  42 kly from MW center  Merging with MW  Discovered in 2003  42 kly from MW center  Merging with MW

Milky Way Ring  Thick ring of stars beyond disk

Milky Way Ring  Due to past galactic collision? Which of these galaxies passed through one to left? Star formation in ring of shocked gas

The Local Group  More than 54 galaxies  Mostly dwarfs, including those merging with the Milky Way  3 Major spiral galaxies  Milky Way, Andromeda & Triangulum  More than 54 galaxies  Mostly dwarfs, including those merging with the Milky Way  3 Major spiral galaxies  Milky Way, Andromeda & Triangulum

Polaris Pointer stars point to … Alpheratz Scheat Almach L ITTLE D IPPER B IG D IPPER C EPHEUS C ASSIOPEIA Algenib Markab Rasalmothallah Capella Algol  Cephei A NDROMEDA P EGASUS Enif The Sky Tonight Andromeda Galaxy Triangulum Galaxy T RIANGULUM A RIES Great Square of Pegasus P ERSEUS

Alpheratz Almach Rasalmothallah A NDROMEDA Finding Galaxies Andromeda Galaxy Triangulum Galaxy T RIANGULUM

Andromeda Galaxy  Local Group’s Largest Galaxy  One Trillion Stars (10 12 )  2.5 million light-years away  1.5 x mi (1 ly = 5.88 x10 12 miles ~ 6 trillioin)  200,000,000 M  black hole in center  Approaching us at 300 km/s (190 miles/sec)  Should collide with Milky Way in ~4 billion years  Local Group’s Largest Galaxy  One Trillion Stars (10 12 )  2.5 million light-years away  1.5 x mi (1 ly = 5.88 x10 12 miles ~ 6 trillioin)  200,000,000 M  black hole in center  Approaching us at 300 km/s (190 miles/sec)  Should collide with Milky Way in ~4 billion years

M110 – Dwarf Galaxy M32 – Dwarf Galaxy

Triangulum Galaxy  Pinwheel Galaxy (M 101)  40 Billion Stars (10 10 )  3 million light-years away  1.5 x mi (1 ly = 5.88 x10 12 miles ~ 6 trillioin)  Linked to Andromeda by streams of stars and neutral hydrogen  interacted with Andromeda 2-8 by ago  will have more violent interaction in 2.5 my  may participate in collision with MW  Pinwheel Galaxy (M 101)  40 Billion Stars (10 10 )  3 million light-years away  1.5 x mi (1 ly = 5.88 x10 12 miles ~ 6 trillioin)  Linked to Andromeda by streams of stars and neutral hydrogen  interacted with Andromeda 2-8 by ago  will have more violent interaction in 2.5 my  may participate in collision with MW

The Coming Collision