Timeline 5/4/17. Our Schedule and Topics

Transcription

1 ASTR 1040: Stars & Galaxies Cosmic Web Prof. Juri Toomre TAs: Piyush Agrawal, Connor Bice Lecture 30 Thur 4 May 2017 zeus.colorado.edu/astr1040-toomre Our Schedule and Topics Final Exam on Wed May 10, 1:30pm- 4:00pm, here, closed book, 2 crib sheets allowed (4 sides), bring pencils All observatory reports, virtual or actual project A, due D2L dropbox by Mon May 8 After first three minutes in our universe Computer models of cosmology in action Cosmic web of galaxies emerges: cold dark matter crucial to structure formation Current big outstanding questions or issues in astronomy OVERVIEW 1 billion years 380,000 years 3 minutes Evolution of Universe During first 3 minutes Making the elements How much DEUTERIUM made depends on density of ordinary matter (baryons) Sensitivity in making the light elements Big Bang Gravity freezes out Strong Force freezes out Timeline Matter consists largely of quarks, electrons, positrons, & neutrinos Weak Force freezes out Quarks combine into protons, neutrons, & their antiparticles Virtually all anti-matter is annihilated. Fusion creates Helium Neutral atoms form, light decouples from matter (Cosmic Microwave Background) Very good but complex: Fig

2 After first 3 minutes RADIATION ERA --> 380,000 yr MATTER ERA After recombination : Finally cool enough for electrons to combine with nuclei to form atoms (380,000 yrs) Photons now decoupled = free to become CMB of future Universe becomes transparent to light Era of Atoms CMB 14 billion yrs 10 #$% seconds K 10 $3 K 3000 K 10 4 K K K Era of Atoms 380,000 1 billion yr < 3000 K Cool enough that neutral atoms form through the joining (recombination) of protons and electrons. Matter: neutral atoms Once the electrons are not free to scatter photons, the photons could move freely. General Theory of Relativity was giant step forward, but then Alarming ideas like: 1: expanding universe (Hubble) 2: CMB (big bang) 3: 1 part in 100,000 uniform (inflation) 4: white dwarf SN (dark energy) These could trouble even Einstein! Observational Pillars of Big Bang Theory 1. The universe is aglow with thermal radiation, the Cosmic Microwave Background (CMB) REMINDER 2. The observed abundances of light elements agree with Big Bang predictions 3. The universe is expanding 4. The night sky is dark 2

3 Era of Galaxies Z ~ 20 Forming first stars and galaxies About 1 billion years after Big Bang, first stars and galaxies start to form And we ve been there ever since SIMULATIONS Simulating large-scale structure Forming filaments in cosmic fabric Kravtsov COLD DARK MATTER GALAXY CLUSTERING Evolve and rotate viewing Co-moving frame in overview 3

4 Simulation: Dark matter structure now Gravity of cold dark matter causes clumping Overdense regions pull in more dark matter 140 M ly across Dark matter cosmic web Forming galaxy clusters Web of 3 million real galaxies in sky Galaxy clustering in ever deeper surveys ~ 30 degress across 4

5 Galaxies are always moving: Hubble flow + respond to local clustering Gravity is still at work Dark matter is still pulling things together. After correcting for Hubble's law, galaxies are currently flowing toward the densest regions of space. Milky Way at center is moving toward Virgo cluster, then Coma supercluster 600 M ly across The Big Mysteries What will be the fate of the universe? What is the universe made of? What is the dark matter? Is the theory of inflation correct? What is the dark energy? Which of this, if any, should we believe? Science is not about belief, it s about exploration SIZE Models of universe and its fates White-dwarf SN NOW OPEN TIME REMINDER CRITICAL (FLAT) CLOSED Some say the world will end in fire Some say with ice From what I ve tasted of desire I hold with those who favor fire But if I had to perish twice I think I know enough of hate To say that for destruction ice Is also great And would suffice -- Robert Frost National Poet Laureat 5

6 Andromeda surprises with Spitzer in IR NGC205 A final visit to our nearest big neighbor: Andromeda M31 M microns (blue), 4.5 (green) 8 microns (red) M31: 11,000 image composite with Spitzer M31: Forensic evidence of galactic collision M32 plunged through disk on polar axis ~210 My ago?? 1 Striking rings of dust and starbirth 2 Ring splits into two, forming hole on lower right 3 Delicate tracings of spiral arms into very center M31: Beautiful neighbor in UV and IR We wish you good fortunes with the Final Exam next Wed (1:30pm here) -- please bring pencils, crib sheets, ID GALEX: SPITZER: Far-UV (blue) young hot massive stars Near-UV (green) relatively older stars 24 micron IR (red) cool, dusty star forming and we hope you ve enjoyed this course that has touched the universe 6