ASTRONOMY 3303   HW#4     due Wed Oct 04, 2017

Print a copy of this page and enter it in your portfolio. Answer the questions (preferably type them or write legibly) separately; make sure to include the graded answers in your portfolio after they are handed back. In all cases, be sure that you give complete derivations, showing the equations you use, including the values of any constants you use and always giving the units involved.


Part I: The NASA Extragalactic Database NED
For this assignment, we will investigate the galaxies in the vicinity of the nearby "poor" cluster known as MKW 11. Use the NED to record relevant information about the cluster and to answer these questions

Part II: Running a search using the SDSS SQL
Let's investigate the photometric dataset available from the Sloan Digital Sky Survey (SDSS) in the region of MKW 11. Before you begin, take a look at the SDSS SQL help page and review the instructions on how to run a SQL search of the SDSS database.

Below is the SQL search you should run; be sure you understand the syntax.
SELECT
 p.ra, p.dec,s.z,p.petroMag_g,p.petroMag_i,p.modelMag_g,p.modelMag_i,
 p.lnLExp_r, p.lnLDeV_r, s.zWarning,p.objID
FROM PhotoObj p, SpecObj s, SpecLine l
WHERE
 p.SpecObjID = s.SpecObjID AND
 p.SpecObjID = l.specobjID AND
 s.specClass=2 AND
 l.lineID = dbo.fSpecLineNames('Ha_6565') AND
 p.ra >=198. AND p.ra <= 207. AND
 p.dec >= 7. AND p.dec <= 16. AND
 s.z <= 0.061
order by p.ra

Figure out what all the parameters listed above are, and how the SQL search is going to work.


Part III: The CMD of galaxies in the MKW 11 region
Next, let's explore the CMD of galaxies included in the SDSS in the region of MKW 11 to a larger sample covering 420 square degrees of sky covering the Coma supercluster and its member groups and clusters of galaxies as presented in Gavazzi+ (2010), A&A 517, 73 and shown here to the right. Taken from Fig. 3 of that paper, the figure shows the "g-i color versus i-band absolute magnitude relation of all galaxies in the C[oma]S[upercluster] coded according to Hubble type: red = early- type galaxies (dE-E-S0-S0a); blue = disk galaxies (Sbc-Im-BCD); green = bulge galaxies (Sa-Sb)... Contours of equal density are given. The continuum line g-i = -0.0585 *(Mi + 16) + 0.78 represents the empirical separation between the red-sequence and the remaining galaxies. The dashed line illustrates the effect of the limiting magnitude r=17.77 of the spectroscopic SDSS database, combined with the color of the faintest E galaxies g-r ~0.70 mag.."


Click for a larger view.
Figure 3 from Gavazzi+ (2010)


Part IV: Group discussion: Active Galaxies.

In class, we had a detailed discussion about star formation in galaxies, and signs of activity. Let's have a closer look at one case with some interesting new data, based on an ESO press release.

We will discuss active galactic nuclei in more detail in the following lectures, so don't worry if you do not yet fully understand the terminology used here.

Based on what you have learned in class, discuss with your group the relevance of these observations, and what you find most interesting about them. What is the VLT telescope? At what wavelengths does it observe, and why? What made these observations challenging? In what ways is this galaxy different from the Milky Way? What can we learn from studies like this one? Using the astronomy query tools you have encountered so far, try to find more information on this galaxy. Use at least one scientific publication with different data in your discussion. Also, as a group, be prepared to give a 3 minute summary of your discussion during the lecture on October 4th, as a lead-in to discussing your findings with the other groups. It may be useful to assign a discussion leader and a note taker within your group. If you require any form of media, please prepare handouts or anything equivalent that is suitable for sharing at the table. Also, please provide a brief (1-2 page) write-up of your discussion.
NOTE: Self-organize in groups of up to 3 students for this discussion. Clearly indicate and give credit to all members of the discussion group, and clearly reference all source materials you consider in your discussion (e.g., specific parts of the press release, newspaper articles based on this release, the textbook, class notes, etc.). You may hand in only one copy of the report for your group if preferred, but make sure that all names are provided!