Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula...
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![Page 1: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/1.jpg)
Measurements
• Magnitudes– Apparent magnitude (m)– Absolute magnitude (M)Distance modulus formula
m-M = -5 +5 log (d) d in pcm-M == distance as given by magnitudes
m-M = 10 d=1000 pcm-M = 20 d=105 pcm-M = 30 d=107 pc
![Page 2: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/2.jpg)
M related to luminosity
Typically luminosity not often quoted.
Filters
Johnson UBVRIJHKL
Mv = Abs. V magnitude
V = App. V magnitude
B = App. B magnitude
Colors
B-V, U-B, etc
Temperature
Dust
WattsL
M
L
L
MML
LLog
sun
sun
MM
Sun
sunsun
sun
26
)(04
1086.3
85.4
10
)(4.0
![Page 3: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/3.jpg)
• Spectra– Radio– Microwave– IR– Visible– UV– X-ray– Gamma-ray
• Environment• Non-thermal –
Synchrotron• Spectral Features
– Absorption– Emission– Continuous
![Page 4: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/4.jpg)
Velocity - Redshift
Low Velocity - Doppler shift formula
z is the Redshift (usually)
z used as a distance indicator
High Velocity – Relativistic Redshift formula
lab
labobs
lab
labobs
z
skmv
/000,300
skmz
zv /000,300
11
112
2
![Page 5: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/5.jpg)
Scales of Distance
AU = Astronomical Unit = 150 million km
Parsec (pc) = 206,265 AU = 19 trillion miles
Lightyear = 0.307 pc =5.9 trillion miles
1 pc = 3.26 lightyears
![Page 6: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/6.jpg)
Milky Way – 100,000 ltyr, 30,000 pc
100 kilolightyears, 30 kiloparsecs (kpc)
Largest galaxies = 10 x MW
Smallest = 100 pc
Sun – MW center = 7.5 kpc
Local Group = 3 million light years
= 1 Mpc
![Page 7: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/7.jpg)
Galaxy Classifications• Hubble’s Tuning Fork
Sa Sb Sc Sd
SBa SBb SBc SBd
E0 E6 S0
Irregulars
![Page 8: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/8.jpg)
Ellipticals
• E#
# = 10 (a-b)/a
• No systematic rotation axis
• Random star motion
b
a
![Page 9: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/9.jpg)
cD galaxies
• Largest
• Brightest*
• Diffuse
• Multiple nuclei
• Few Mpc size
• Centers of clusters
![Page 10: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/10.jpg)
Spirals
• S and SB
• Tightness of arms
• Size of bulge
• Sloppy arms
![Page 11: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/11.jpg)
Barred Spirals
• Why?
• Not always visible
• Secondary/tertiary
• 25% - 65% of spirals(!)
![Page 12: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/12.jpg)
S0 - Lenticular
• Spiral-less spirals
• Disk, no structure
• Bars
![Page 13: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/13.jpg)
Irregulars
• Irr I – OB Stars– H II regions– Population I
• Irr II– Just plain weird
![Page 14: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/14.jpg)
Sm & Im Irregulars
• Magellanic cloud like
• Sm – spiral like
• SBm – barred spiral
• Im - small
![Page 15: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/15.jpg)
Dwarf Galaxies
• Irregulars (dIrr)
• Ellipticals (dE)
• Spheroidals (dSph)
![Page 16: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/16.jpg)
Gerard de Vaucouleurs
• Sm, Im
• Degrees of Bar-ness
A - B
• Degrees of Ring-ness
s - r
![Page 17: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/17.jpg)
![Page 18: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/18.jpg)
![Page 19: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/19.jpg)
![Page 20: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/20.jpg)
![Page 21: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/21.jpg)
![Page 22: Measurements Magnitudes –Apparent magnitude (m) –Absolute magnitude (M) Distance modulus formula m-M = -5 +5 log (d)d in pc m-M == distance as given by.](https://reader035.fdocuments.in/reader035/viewer/2022062802/56649eaa5503460f94bae79e/html5/thumbnails/22.jpg)
Other measurements
• Sizes – poorly known
• Luminosity
Classification I – V
Wavelength dependent
Galaxy type, structure, content, history – all interrelated – how?