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| Classifications of Galaxy Morphology? |
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Definition
| Bulge to Disk ratio, lumpiness of spiral arms, tightness of spiral arms |
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| "a" has a larger bulge, tighter arms, and less dusty gas |
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| tightly wound arms, big bulge |
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| lumpy, open arms, small bulge |
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| no bulge, disorganized, lumpy |
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| Morphology stats (vol limited) |
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| .33 spiral, .54 irregular |
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| Dirr most common, DE high density regions, Dsph faintest |
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| Color, Stellar Pop, Gas content of Elliptical? |
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| Color, Stellar Pop, Gas content of Lenticular |
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| (in between E and Spr): Greenish, Old and Intermediate, modest gas content |
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| Color, Stellar Pop, Gas content of Spiral |
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| Blue, old + int + young, high gas content |
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| Color, Stellar Pop, Gas content of Irregular |
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| Bluer, mostly young, unpredictable gas content |
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quantify surface brightness as function of position (radially along major axis).
leads to mass distribution |
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| Intensity (I or capital Sigma) |
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Definition
Surface Brightness (I or cap sigma) = Luminosity / Area = flux / angular area;
u = mag of 1 arcsec^2 patch; |
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| line of constant surface brightness |
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| Exponential Surface Brightness (r) = ? |
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Definition
| Ee * e ^ (-1.679((r/re) - 1)) |
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| de Vauc Surface Brightness (r) = ? |
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Definition
Ee * e ^ (-7.67 * ((r/re)^(1/4) - 1 ))
where re = radius w/ half light
Ee = E(re) |
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| E(r) = Ee * e ^ (-k((r/re)^(1/n) - 1)), where K is coupled with n; for n = 1, k = 1.679; for n = 4, k = 7.67 |
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| use scale length( n for disk); find r where E(r) falls below some limit, eg. r = re |
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| integral from 0 to r of I(r) * 2pir * dr |
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| a --> c; younger, opposite of late. |
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| explore parameter space, create statistical samples, search of particular obj or phenomena |
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| A * omega = 4 * pi * r^2 * (solid angle in deg^2) |
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| biased towards most luminous; # depends on density and volume surveyed; if density constant --> N ~ L^(3/2) |
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| (IMF) Use of Schechter Function? |
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Definition
#(M1,M2) = integral from M1 to M2 of schechter function phi(M) or phi(L).
Mt(M1,M2) = integral from M1 to M2 of squiggle(M) where squiggle(M) = M * phi(M)
generally (integ of salpeter IMF) |
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Definition
function for number of stars in a galaxy.
phi = squiggle / M |
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| most mass in low mass stars; most L in high mass stars; color depends on mean age of stellar pop. |
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| stellar population synthesis |
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Definition
| IMF + isochrones/evol. trails + lib of stell. spectra = spectral evol of single burst of SF |
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| burst = brightens --> fades; const. SFR = const UV spectra, build up of red/optical/NIR |
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| initial UV from O and B stars, massive dominate; after long while shrinks and reddens; post burst is dominated by A type (.5 Gyrs) |
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| Sections of Interstellar Medium? |
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Definition
| Hot ionized gas(HII), neutral atomic gas(HI), cold molecular gas(H2 or CO), dust |
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| Detecting sections of ISM? |
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Definition
| HII --> Halpha; HI --> 21cm line; molecular gas --> mostly CO rot. line, H2; Dust --> Blackbody Radiation |
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| rank ISM components by density (low to high) |
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| 1) hot ionized gas (1/2 atoms /cm3); 2) neutral atomic gas(1-10 atoms / cm3); 3) cold molecular gas(10^2 - 10^5 atoms / cm3; 4) dust (solid) |
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| ISM component proportions by most common? |
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Definition
| 1) neutral atomic gas 65%; 2) cold molecular gas 20%; 3) hot ionized gas 15%; 4) dust <5% |
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| med cold ( between neutral atomic gas and cold molecular gas ) |
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| recombination of electron from n = 3 to n = 2 emitting photon with wavelength 6563 angstroms |
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21cm wavelength emitted from change to parallel to antiparallel spins; smallest energy;
galactic plane; extends past stars |
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| quantization of angular momentum |
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| scatters blue light; transparent to red light; extinction and reddening; emits IR from absorbing UV/V |
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| Halpha; compact region of SF; cna be in spiral arms; |
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| HIneutralhot --(compressed/cooled)--> H2molecular --(ionization by O stars)--> HIIionizedhot --(massive stars die, recombination)--> HIneutralhot |
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| Structure of HII region? (r from 0 to r) |
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| H2(new stars) --> HII --> Dust --> HI |
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| mass of stars / time of universe |
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| Esfr = (2.5 E -4) * (Egas)^(1.4) |
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| Purpose of Global Schmidt Law? |
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| determining star formation rate per unit area |
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| SFRefficiency * (density of gas) ^ (1.5); SFReff = Esfr / Egas |
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| Components of Galaxy Kinematics? |
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| Rotation and Velocity dispersion |
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| random, dominant in ellipticals |
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| (vdisp)^2 = (1/N) sum from 1 to N of (Vi - <V>)^2; where Vi is observed velocity; |
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| Vobs = Vcsin(i) where i is inclination and Vc is rotation velocity |
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| determines mass distribution |
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| 90% of galaxy mass, probably huge |
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| NFW profile --> p(r) = p0 / ((r/rc)(1+(r/rc))^2) |
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Vc^2 = (Vc,DM)^2 + (Vc,bulge)^2 + (Vc,star)^2 + (Vc,gas)^2
Vc observed, Vbulge,star,gas from surface density |
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| How to get rotation curve? |
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Definition
1) stars
-measure surface photometry
-convert to surface density using appropriate M/L
2) Gas
-measure HI surface density
-add correction for metals and molecular gas
3) Dark Matter
-subtract first two components
-fit function for DM density profiles |
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| context of Tully-Fisher Relation? |
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Definition
| Luminous galaxies have higher max Vc |
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Definition
L prop to (Vc)^N N = 3,4
M(abs) = C - 2.5*N*log10(Vc);
more accurate with inclusion of gas |
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| conclusion of tully-fisher? |
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Definition
| faster rotation = more massive = more luminous; implies mass of Baryons through luminosity and velocity --> Vflat^2 = G*Menc / rmax |
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| slow moving; interacts only through gravity; WIMPs or Axions. |
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| Elliptical Galaxy Kinematics? |
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Definition
| V is mostly random, therefore V = vdisp; Vdisp is anisotropic; some with kinematically distinct cores; vdisp rises to center; |
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| M prop V^2 * R / G; for ellipticals? M prop vdisp^2 * R / G; |
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| n = M / R^2 = V^2 /G * R; REVIEW WITH FUNDAMENTAL PLANE |
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| Fundamental Plane theory vs observed? |
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Definition
theory : R prop E ^ -1 * vdisp ^ 2;
obs: R prop E ^ -0.8 * vdisp^1.53 |
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| Cause for error between theory and observed fundamental plane? |
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Definition
1) M/L not constant at all masses
2) structure non-homologous (e.g. ellipticals are not self-similar versions of each other)
3) Measurements are not consistent for all galaxy sizes |
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Definition
E = V^2 / G*R*Y; E*R/V^2 = const., where const depends on M/L;
allows for trace of evolution of stellar mass/light ratio with time/redshift |
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| Evol. of FP with redshift? |
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Definition
-assume structure of ellip. same at all redshifts and stars formed long ago
-stars fade as bright massive stars die
- same mass, lower L, M/L increases with time |
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| Galaxy Formation Constraints? |
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Definition
Spirals:
-formed from gas accretion with high angular momentum
- gas --> stars
Ellipticals:
-repeated random mergers of gas and stars
-gas streamed to center forming high density of stars |
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| how does reionization affect galaxy evolution? |
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Definition
| intense UV in early universe keeps gas too hot to form low mass galaxies |
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| How does "feedback" affect galaxy evolution? |
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Definition
feedback - energy input from within galaxy drives out gas or shuts down accretion
-SN - starburst - lots of SN in same location
-AGN - central BH accretes gas, emits light, powers jets, injects energy into surrounding gas |
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| how are galaxy mass and CBH mass related? |
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| High L makes galaxy look like star, from washing out of galaxy light |
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| luminous QSOs w/ radio emission and maybe radio jets |
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| broad emission lines; blue; depends on viewing angle. |
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| most massive gravitationally bound structures in Universe; too fast to stay together w/o DM |
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Rich = 30-300 bright galaxies
poor = 5-10 bright galaxies (local group) |
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virial theorem --> Mtot = (5/3) R * vdisp^2 / G
- 10 - 30% gas; hot ionized >10^7 K
- metals
- gas blown out or stripped away from other galaxies |
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| Exogalactic Distance Ladder |
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| radar (SS) --> stellar parallax (nearby stars) --> spectroscopic parallax(MW) --> Variable stars (nearby galaxies) --> TullyFisher --> Standard Candles (galaxies and galaxy clusters) |
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| Distance through MS fitting? |
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Definition
| apparent mag prop L/4pid^2; compare apparent mags with constant L; |
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| distance through variable stars |
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Definition
1) measure period
2) derive luminosity
3) measure apparent brightness
4) derive distance |
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| distance through TF relation |
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Definition
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| distance through fundamental plane |
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Definition
| compare angular size to physical size R derived from vdisp and E surface brightness; estimate L for galaxy using cluster |
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extreme L common among type 1a;
measure apparent brightness; derive d |
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light curve: broader is brighter; more L --> fades slower;
Mmax,B = -21.726 + 2.698*deltam15b; |
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1. Random
-use average to reduce
2. systematic
- offset in one direction
- miscalibration
- fix by improving calibration
- fix by using galaxies at large distances. |
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