Scavenger Hunt: The 2005 dataset:
To get you started into thinking about galaxies that ALFALFA might
or might not detect, we'll use a group of interesting objects contained
in the observational dataset obtained by the 2005 Summer Undergraduate
ALFALFA team at the Union College Workshop.
- Take a look at their
list of 12 galaxies and the set of links to different
galaxy databases. Each line contains the following information on each galaxy:
Cornell EGG galaxy catalog entry number, optional name (where applicable),
position in J2000 coordinates (hhmmsss+ddmmss), RA and Dec in degrees,
and then links to sites at the SDSS, Skyview, the DSS2 (blue and red) and NED.
Sometimes two views are given (0.03 degree on a side, and .1 degree on a side).
Learn what is in these catalogs/databases and how to manipulate them.
- In particular, learn
about the Sloan Digital Sky Survey and its photometric and
spectroscopic components. What can you learn about galaxies like these
from the SDSS data?
- SDSS will produce optical fluxes and positions for 100 million
objects and will obtain spectra for 1 million objects. How do
the SDSS folks decide which of the 100 million objects to target
for the spectroscopic observations? In fact, Martha tells us that
(a) not all galaxies end up in the SDSS spectroscopic target
lists; even bright ones sometimes don't make it; (b) sometimes,
more than one spectroscopic object is contained within a single
galaxy. Why might this happen?
- Over what portion of the galaxy are the spectra obtained? Is the
answer important to us?
- What spectral features are found in the spectra of the 12 galaxies?
How can you interpret the spectra in terms of the probability that
the galaxy will be detected by ALFALFA?
- Comment separately on the appearance of the SDSS (a) image(s) and
spectra for each of the 12 galaxies. Do you expect to detect all
12? Why or why not?
Investigate the information contained at the other links. What's
useful about them? Is there anything that is particularly unusual
or noteworthy about any of the galaxies?
Last modified: Sat Oct 6 11:36:00 EST 2007 by martha