Problem set 1 for ASTR 323/423: The Local Universe
Due in class, Wed Jan 23
Individual problems:
(1) Galaxy classification
Get your hand in by going to http://www.galaxyzoo.org.
(2) Sandage "The Hubble Atlas of Galaxies" pp 7-26 gives a detailed
description of the traditional Hubble classification. Using this as a
guide and more galaxy images from the Sloan Digital Sky Survey, this
time using the Navigator function
(http://cas.sdss.org/astro/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, and any
difficulties you had applying Sandage's rules.
RA=221.546, Dec=-0.223 (Steven J)
RA=145.514, Dec=0.336 (Lucy)
RA=39.849, Dec=1.094 (Meredith)
RA=36.907, Dec=-1.155 (Ethan)
RA=152.1104, Dec=12.3 (Colin)
RA=187.455, Dec=8.0 (Stephen R)
Another galaxy of your choice near the above galaxy. Give RA and Dec
and print out an image. (Jen and Lauren; make sure you dont choose the
same galaxy)
The person whose name is after each galaxy's coordinates will give a
short presentation in class (first 4 on Wed 23rd, rest on Fri 25th)
justifying your classification.
(3) Graduate students only, group problem:
There have been many attempts to improve on galaxy classification
schemes such as the Hubble classification. As well as other
morphological methods, there has been a movement towards developing
less subjective, more repeatable methods, and ones which are more
closely tied to physical principles. Read the following papers and
write a 3-4 page critical review of the alternatives to morphological
classification, and which ones you feel are particularly useful in
terms of (a) feasibility and repeatability and (b) possible
connections to theories of galaxy formation. (I will be grading on
quality of writing as well as content.)
Sandage ARAA 43, 581 (2005) puts the case for a purely morphological
classification.
You can earn extra credit by finding and discussing recent useful
articles on this topic.
Read The Science (http://galaxyzoo.org/Project.aspx) and then do the
Tutorial and Proceed to the Trial. After you have passed the Trial,
classify 15 galaxies and print out the summary you get by clicking the
Show My Galaxies tab.
Contrast this with Ensellem et al 2007 MNRAS 379, 401
Balogh et al 2004 (ApJ 615, L101)
and Blanton et al 2002 (ApJ 594 186).
Finish with a combined technique by Conselice 2006 (MNRAS 373, 1389).