Problem set 2 for ASTR 323/423: The Local Universe

Due in class, Wed Sept 20.

Individual problems:

(1) Galaxy classification

Sandage "The Hubble Atlas of Galaxies" pp 7-26 gives a detailed description of the traditional Hubble classification. Using this as a guide, and using galaxy images from the Sloan Digital Sky Survey, via the Navigator function http://skyserver.sdss.org/dr13/en/tools/chart/navi.asp (type in RA and Dec in degrees in the window), decide the Hubble classification of the following galaxies, print out an image to hand in, and write a short paragraph explaining why you chose this classification. You should include comparison galaxies in the Hubble atlas which you used to classify each galaxy. Note any difficulties you had applying Sandage's rules.
It may be helpful for you to type the NGC numbers of some of the Hubble Atlas galaxies into Navigator so you can see, for example, what HII regions look like in color images, etc.
Note: all students classify all galaxies, students will be chosen at random to give a presentation on one galaxy in class.

(a) RA=221.546, Dec=-0.223
(b) RA=145.514, Dec=0.336
(c) RA=39.849, Dec=1.094
(d) RA=36.907, Dec=-1.155
(e) RA=152.1104, Dec=12.3
(f) RA=161.957, Dec=12.582
Another galaxy of your choice near one of these galaxies. Give RA and Dec and print out a color image.

(2) This problem should be done in groups of 2-3 undergrad students, and individually for graduate students. Groups should include a paragraph at the end describing which student did what.
Morphological classification can only get us so far, and is particularly difficult to implement for "look back" studies of high redshift galaxies. Find a recent paper (after 2000 when SDSS data became available) which describes the measurement (in low redshift galaxies) of one of the following galaxy properties: color, star formation rate, metallicity. Explain how the measurement is made (do you need spectra or only imaging? etc), what are sources of random and systematic error, and give a critical appraisal of this technique as (i) a way of classifying galaxies and (ii) a way of constraining their formation and/or evolution. Run your chosen paper past Prof Morrison first.