Session 10 Classifying Galaxies & Distance Ladder PDF

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Professor Mario De LeoWinkler...

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Classifying Galaxies & Distance Ladder 4/27 (session 12) Pop II- exists in bulge- yellow, red color ● Globular clusters Anything that is NOT hydrogen/helium- a metal ● Metal rich= rich in oxygen, carbon 1st person to do a classification on the galaxy- Hubble’s Classification Scheme https://ilearn.ucr.edu/webapps/blackboard/execute/content/file?cmd=view&content_id=_3212749_ 1&course_id=_268211_1 Slide 4  ● Based on their form in visible light ● TUNING FORK ○ Elliptical galaxies (on the left)- E- the higher the number, the longer the galaxy ○ S0- lenticulars-in the middle ○ Spiral galaxies- Sa-c (on the top) ■ Bulge, disk, spiral arms ○ Spiral Barred galaxies- SBa-c ■ On the bottom of the tuning fork ○ Bottom left- irregulars ● **DOES NOT imply evolution Spirals ● Pop II in bulge Core- SUPERMASSIVE red old stars ■ Overtakes color in bulge- bulge is yellow ● Pop I in disk ○ 70% of the disk is dwarf red stars (dim) ○ Overtaken by newly created new stars (Pop I) ● Mass 10^9-10^11 M. (lenticulars) - 70% of our galaxies are SPIRALS- beginning of universe-not as many spirals - Supermassive black hole in the center - Star formation along disk - Stars, dust gas- same pattern along center Sa Big bulge Tightly wound arms A- VERY tightly wound ● Woolly- where the other starts, when it ends Small amt of gas in arms Sb Smaller bulge

LOOSER arms MED amt of gas Sc SMALLEST bulge Very loose arms ● You CAN make out spiral arms Large amounts of gas Spiral Barred Galaxies SBa 66% of all spiral galaxies have bars ● Relationship w spiral arms **Too much dark matter- no bar forms ● ● ● ●

Indistinct arms Big bulge Tight arms SMALL amt of gas

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Big bar Smaller bulge Looser arms Med amt of gas ○ ** OUR GALAXY

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Smallest bulge Very loose arms LARGE amt of gas

SBb

SBc

Spiral stars go around stably Ellipticals Can MUCH smaller than MW- dwarf sphericals or MUCH bigger ● Can be MOST MASSIVE of galaxies ● 20% of all galaxies in Universe ● NOT presently forming stars ○ ONLY old stars- no gas, dust, ● Stars are going RANDOMLY around centered

How elongated- classified Supermassive hole in center-biggest black hole ● Billions of times the mass of the sun ● Made of METAL POOR pop II stars E0 ●

Old & compact in center

E4 ● No structures **Game w. The type of pop stars? Dwarf elliptical ● Similar Lenticulars Disc galaxies ● NO GAS- still have DUST ● OLDER than spiral galaxies Spirals have to form more recently to look like that ● BIG, no star formation Irregulars ● Dominated by dark matter ● 3% of galaxy ● ***DARK MATTER IS EVERYWHERE ○ Allow them to create new stars- bluish in color ● No structure ● Smaller in mass ○ Refer to table Refer to Slide 50 https://ilearn.ucr.edu/webapps/blackboard/execute/content/file?cmd=view&content_id=_3212749_1&c ourse_id=_268211_1 DISTANCE SCALE Far away galaxies need different techniques ● Close to the center of our galaxies ○ R.R. lyrae ○ Further places ■ Telegalaxies ■ supernovas

Parallax- if you know the distance between the 2 places you’re looking & ANGLE of difference Stars that have relationship btw. Pulsation period & distance ● R.R. lyrae ● Standard candle Tully-Fisher relationship- SPIRAL GALAXIES ONLY ● Faster the galaxy spins- brighter it is Supernova type 1a ● Reaches exactly the SAME PEAK BRIGHTNESS ● Same dimming pattern ● Determine distance/amt of dust to the SN Happen very rarely in galaxy...