Things to do to get science out of ALFALFA
Note: see also "Computing Galaxy Properties for ALFALFA" internal link for detailed directions to use existing programs (ask Becky for link).
Available datasets
- ALFALFA grids
Martha will provide you with the ALFALFA Level II data products
corresponding to several ALFALFA grids which cover the region
of your target group. These will include the grids themselves as
well as the "src" and "ps" files and that source catalog. So the first
thing to do is to learn what all these things are, what they contain,
and how to use them. Among other things, learn to use "gridview"
and "galcat". The Siena group is working on docuementation
Getting Started in ALFALFA, including a summary of gridview.
(Two notes: (i) you will probably not need to learn
much about galflux and (ii) HI deficiency method is under construction.)
- The AGC
Your IDL installation comes with a recent version of the
AGC
the misuse of which will insure you a free delivery of a pair
of
cement shoes. Make sure you understand what the AGC is (and
isn't!). It is an incredibly useful database, but you need to understand
its limitations. We suggest you have your students experiment with it, both
in the region of your group and in general. Among other things, learn to
use "agcbrowse" and "plotalfa" to investigate the distribution of galaxies
in the region of your group.
- The SDSS
In order to be able to understand the history and environment of
the galaxies that ALFALFA does and does not detect, it is really
useful to study the same region using the SDSS. So learn to use
it and understand what it contains.
- Here is some IDL code to read various catalogs.
Things we need to do
- Understand ALFALFA's limitations
- What are the limitations of ALFA's angular resolution? What
is the **linear** angular resolution at the distance of your
group?
- Why might you "find" a galaxy in a grid but not in the
ALFALFA catalog?
- What are sidelobes? What impact can sidelobes have?
- Determine group membership Mary
- Using the AGC and NED to identify structures
- See
Giovanelli et al 1997 (Figures 2+) and apply their method on your
group/cluster.
- Calculate distances
- Understand when and why Hubble's law doesn't work!
- Understand what primary and secondary distance indicators are.
- Understand what the velocity frame of the CMB is and how it is
determined.
- Understand what a peculiar velocity is.
- Understand what a flowmodel is.
- The EGG flowmodel routines are now in LoveData. Be sure
to understand the uncertainties in distances!
- Correct optical magnitudes for various effects
- Correct for galactic extinction
- Understand what galactic extinction is and what methods are used
to derive it.
- Understand the DIRBE instrument and data set and how it can be
used for galactic extinction.
- The EGG DIRBE routine (coming soon) EGG
- Correct for internal extinction
- Understand what the correction for internal external extinction is.
- Correct for K-correction Rose
- Find the X-ray data Aileen
- RASSCALS
- Other
- What does X-ray tell us?
- Find HI deficiencies Becky
- References
- Becky has program to compute Solanes et al 1996 HI def.
- Calculate properties
- Distances (Use distance to group as whole for all galaxies.)
- HI masses
- Optical luminosities
- Global colors
- Stellar masses Rose
- Radio continuum luminosities Aileen and Martha
- Starburst or AGN? Kelley
- Local environment
- Nearest Nth neighbor Mary
- Local velocity dispersion Mary
- Local ICM density Aileen
- Local ICM temperature Aileen
- Documention for everything
If you learn something useful or write a useful program, please share it with the group.
- Useful links
Comments, suggestions, corrections, additions always welcome; write Martha.
But, Martha would also like some help writing documentation for all this!
Last modified: Sun May 16 10:54:30 EDT 2010 by martha