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ASTR3002 ­ Galaxies in the Universe ­ 2008 ­ Assignment_Carollo
Note: this assignment is due 19 September. It has to be presented in time and in a neat way to the lecturer or marks will be deducted. You can also send a pdf version by email to carollo@mso.anu.edu.au

The structures and star populations in the Milky Way [12 points] Daniela Carollo ­ 09/09/08 ­ 12/09/08 ASSIGNMENTS Problem N. 1 a. (1 point) Using the formula of the propagation errors demonstrate the following relation (Lecture N. 1): d/d = /. b. (2 points) Also, given the following spectral type: Main Sequence: Giants: F5 G0 M0 K5 M0

for a given limit magnitude of the telescope mV = 20, evaluate the parallaxes for each spectral type, and give an indication of the galactic structure at which the star could belong. Which space mission of the modern era could potentially measures these values of parallax? Note that:


The absolute magnitudes are available at page 107 of Binney and Merrifield. The parallax must be expressed in µas. Problem N. 2 c. (2 points) Given the following distances: d = 1 kpc, 2 kpc, 4 kpc, evaluate the error on the tangential velocity of a star, assuming a 15% of relative error on the distance, and an error on the proper motions of 4 mas/yr. Repeat the same evaluation for a distance of 8 kpc, and asses if the error obtained is acceptable to use the derived velocity in galactic studies.

Problem N. 3 The table below lists four stars of the Sloan Digital Sky Survey (Lecture 2) Star name
SD SD SD SD SS SS SS SS _449 _314 _165 _509

(deg)
0. 0. 0. 0. 038 090 125 128

(deg)
-8.796 14.747 -10.406 1.218

µcos() (mas) (mas/yr)
0. 0. 0. 0. 364 257 298 340 -6.016 -4.486 2.251 0.928

µ (mas/yr)
-15.694 -3.772 -22.786 -6.766

Vr km/s
-97. -11. -91. -88. 6 5 0 8

d (kpc)
2. 3. 3. 2. 7 9 4 9

d. (2 points) For each star local standard of rest. Use reported in the Lecture N. that of Mihalas & Binney

evaluate the U,V,W velocities in the the relation and matrix transformation 1. The correction for the solar motion is 1981.


In the table: right ascension and declination are in degree parallax is in mas proper motion is in mas/yr radial velocity is in km/s distance in kpc e. (2 points) Evaluate also the rotational velocity in the Galactocentric Reference Frame, and basing on the value obtained place the star in one of the following galactic structures: thick disk, inner or outer halo.

Problem N. 4: f. (1 point) A star with metallicity [Fe/H] = - 2 belong to a Population I or Population II? g. (2 points) The plots below shows two different metallicity distribution for stars in the Milky Way. At which structure of the Galaxy they could be associated? Plot 1.


Plot 2.