L8

Question 1

axis of diff HR dig?

Answer 1

HR: M_abs vs soectral type
CMD: M_abs vs colour
Kiel dig: g vs T_eff

Question 2

REMINDER: GAL MORPHO

Answer 2

X

Question 3

SERSIC PROFILE FORMULA, LABEL

Answer 3

X

Question 4

FIND LUMINOSITY FROM SERSIC PROFILE

Answer 4

X

Question 5

PROJECTION FROM INCLINATION OF CIRCULAR GALAXIS?
MAJOR AXIS?
MINOR AXIS?

Answer 5

R

R COS i

Question 6

PROJECTION FROM INCLINATION OF CIRCULAR GALAXIES: CALC DISTRIBUTION OF APPARENT AXIAL RATIOS

dist of a/b, i.e at what angle are most galaxies on?

Answer 6

del omega: solid angle segment = 2 pi sin i
del mu: b/a = cos i

prob of finding a randomly oriented gal: del omega/del mu = 2 pi = const

gal with diff a/b values are equally distributed

Question 7

are real obs exactly b/a equidistributed (inclination)?

Answer 7

no,

real galaxies are more complex. In particular one has to take into account the effects of dust attenuation at different inclination angles, at least for disc galaxies where the dust is known to be heavily concentrated near the midplane. Early-type galaxies, on the other hand, are usually much less dusty,

Question 8

apparent axis ratio? q?

Answer 8

b/a

Question 9

what oblate vs prolate?

Answer 9

ob: true major axis A
true minor axis: b

oblate: A>B. (—–)
prolate: A

Question 10

derive flatening ratio q for oblate and prolate gal?

Answer 10

end: q_obl^2 = (b/a)^2 = ( (B/A)^2 sin^2 i + cos^2 i)

q_pro = (b/a)^2 = ( (B/A)^2 sin^2 i + cos^2 i)^-1

Question 11

what does it mean for b/a > B/A? oblate

Answer 11

b/a apparent ratio > B/A true ratio

ratio inc = flatness dec becoz for ob A>B

so, apparent flatnesss < true flatness

Question 12

what does it mean for b/a > B/A? prolate

Answer 12

q = b/a > A/B
or q = b/a < B/A

pro: A<b> true flatness</b>

Question 13

explain fig 6.9 on pg 252 sparke

Question 14

isophotes?

Answer 14

contures of const surface brightness