Try to finish this hunt by 5pm so your group can make its presentation right after dinner.
Those people who are not going on the GBT tour should work
on this scavenger hunt Wednesday morning and be ready to help others go through it quickly.
We also suggest that groups may want to have different members work on the different sections
and then share results. |
To the right are the four WAPP spectra obtained from the position switched observations of
the galaxy AGC 310858 displayed with the
horizontal axis in frequency units (top) and then velocity units (bottom). Here, the
ON and OFF-source spectra have been differenced and normalized and the calibration derived
from the CAL-ON/OFF sequence has been applied. In the frequency units plots,
there are interesting positive flux density signals (which we designate by letter)
at 1422.3 MHz (A), 1420.4 MHz (B), 1404 MHz (C),
1381 MHz (D); the 4th spectrum covering the lowest frequency range appears quite different.
Let's try to figure out what these spectra show.     a.   Identify each of the features A, B, C and D in the spectra shown in velocity units. Click here to see a larger version of the first WAPP spectrum, centered at 1415 MHz.     b.   How can you explain Feature A?     c.   What is feature B associated with and why does it appear to be show both positive and negative flux density? Click here to see a larger version of the third WAPP spectrum, centered at 1375 MHz.     d.   Feature D arises from well-known radio frequency interference (RFI). Check out Phil Perillat's list of RFI frequently seen at Arecibo and our own ALFALFA team RFI page. What is Feature D?     e.   Why isn't the transmitter responsible for the RFI at 1381 MHz on all the time? Hint: See our ALFALFA team RFI page. |
Because the RFI transmitter isn't on all the time, we can discard that portion of the
dataset when it is on to produce an RFI-free difference spectrum; because it contains fewer data records,
it will be noiser that one that contained a full 5 min-ON and 5 min-OFF source but it's better than the one contaminated
with the RFI or having no spectrum at all.
The spectrum to the right shows the result of forming the final spectrum after excising the
records with the RFI present.
    f.  
Was the transmitter associated with the 1381 MHz RFI on during the ON-source
or the OFF-source portion of the position-switched observations of AGC 310858? Click here to see a larger version of the fourth WAPP spectrum, centered at 1355 MHz.     g.   What RFI makes the fourth spectrum useless to us? |
Team | AGC number | LBW Spectrum | Links | Notable information/conclusions/oddities/questions |
---|---|---|---|---|
A | 223819 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       | |
  | 180545 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       | |
B | 182595 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       | |
  | 222391 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       | |
C | 322050 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       | |
  | 732152 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       | |
D | 208583 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |
      | |
  | 8847 |
DR9Navi    
  DR14Navi
DSS2blu.03     NED1.0 |       | |
E | 229196 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       | |
  | 193949 |
DR9Navi    
  DR14Navi DSS2blu.03     NED1.0 |       |