|To the right is the LBW spectrum of the galaxy AGC 749542, a code 4 detection
a.   What is a "code 4" detection?
b.   Based on your examination of the spectrum alone, what is the
approximate recessional velocity of this galaxy?
c.   Using only your answer to b., make
a "back of the envelope" calculation of the distance to the galaxy. What more would you need
to know to get a more accurate answer?
|To the right is a spectrum of the galaxy AGC 198363, a code 4 detection in ALFALFA observed
in the standard doppler tracking mode.
d.   Explain what the two features evident in the spectrum are likely to be.
| For our doppler tracking LBW observations, we actually
obtain four different spectra of each target and in the end wind up with two
different final ones.
e.   Explain the differences among first the four, and then, the two.
Be quantitative where relevant (e.g. bandwidth, number of channels, velocity coverage, frequency resolution,
velocity resolution etc.). Remind yourself how the spectral resolutions of these spectra compare to that
of the main ALFALFA survey.
| To the right are the two different final spectra of AGC 198305.
f.   How do the two spectra correspond to the final spectra referred
to in the previous question?
g.   Based on your
examination of the spectra, what is the recessional velocity of this object?
Please, no cheating by consulting other sources!
For fun, take a look at the
SDSS-DS9 image of this object.
Click here to see a zoomed in version of the 2nd one.
| To the right is the LBW spectrum of the galaxy AGC 174577 which was easily detected
by ALFALFA and which was observed by A2669 as a calibrator (i.e., to check that everything was working
and giving the right velocity and flux scales).
h.   What is unusual about the y-axis scale? Why is it that way?
i.   What actor delivered the line: "My Mama always said, 'Life was like a
box of chocolates; you never know what you're gonna get.'"?||   |