Computing resources.
The astrophysics group maintains a small group of Linux
workstations
for beginning graduate and undergraduate students. These
computers are in room 2169 FRH. Students who want an
account on
these machines should see Aaron Barth.
A few general notes: please don't bring food or beverages into
the
computer room. Please try not to touch the flat-panel LCD
screens- they will last pretty much forever if we take good care
of
them, but once they get scratched there's no way to fix
them.
Don't lock the screen on these machines if you're going to be
away from
the computer room for more than a short while. Instead
please log
out so that someone else can use the system.
Printing:
We have 2 HP laser printers for the astrophysics group, one
black &
white and one color. The black & white printer is set
as the
default printer.
Basic Linux/Unix skills.
If you're a beginner, there are various web sites that give
introductory lessons on Linux commands, text editing,
etc.
Here's
one web
site that has a lot of useful information.
The Scientific Linux distribution includes a lot of very useful
software, such
as:
- emacs,
a text editor
- vi, a text editor
- LaTeX, a
document
processing system optimized for mathematical and scientific
papers
- The gcc and
g77 compilers
- Perl
- Python, along with
various useful libraries such as numpy and matplotlib.
- OpenOffice: an
office
suite including word processing and spreadsheets, able to
read MS
Office file formats reasonably well
- Web browsers: mozilla and firefox
- Adobe
acrobat
reader (from the command line, type acroread)
A note about shells: the "shell" is the command language
interpreter
that interprets what you type at a terminal prompt. The
two most
popular shells are
bash
and
tcsh. They
have
somewhat different syntax for scripting and for things like
setting
environment variables. Bash is the default shell for linux
these
days, and most linux manuals will use bash syntax.
However, a lot
of astronomical software that's been around for years has
documentation
written using tcsh syntax. You can use either one and it's
really
a matter of preference. If you're reading the
documentation for a
program and it tells you to issue a command like "setenv X y",
that's a
tcsh command. The equivalent bash command would be "X=y;
export
X". Every time you start up a new terminal
window,
your shell will read either the .bashrc or the .cshrc file (if
you're
using bash or tcsh, respectively) in your home directory.
These
files are where you put definitions for your executable search
path,
aliases, and things like that which you want to be read in every
time
you bring up a terminal window.
Astronomical software installed
on the
student computers includes:
- IRAF: a
general-purpose data
reduction and analysis package distributed by NOAO.
IRAF has horribly
cumbersome syntax, crashes easily, and it's a pretty
confusing language
to script. However, it includes a huge variety of data
reduction
routines that are often the easiest and most efficient way
to perform
certain tasks, and some data reduction packages for the
Hubble Space
Telescope or other observatories are written in IRAF.
There are
manuals here,
most of which are pretty old, but IRAF hasn't changed
much since they were written.
- PyRAF:
This
is a Python-based front-end for IRAF that's designed to be
more
user-friendly than the standard IRAF cl interface.
Once your iraf
directories are set up and working, you can just type
"pyraf" at the
linux prompt to start this up. (See the iraf setup
instructions
above for additional important notes on using pyraf.)
- ds9:
This
is an image-display program that works either as a
stand-alone or as a
display tool for IRAF/PyRAF.
- IDL:
This is an
image-processing environment and programming language.
It's a very efficient language for astronomical data
analysis and very easy to learn.
- sm:
This
is a graphing/plotting program that can read in data from
ASCII
tables, perform mathematical manipulations, and generate
publication-quality plots. The sm homepage has a
tutorial
and a lot of
information about using the program.
Other useful computing
information:
Web resources for astronomy:
- The arXiv
e-print server (known to astronomers as "astro-ph").
Authors can
upload electronic preprints, and each day a list of new
abstracts
appears on the arXiv web site. You can sign up for a
daily email
of new abstracts too. It's good to get in the
habit of at
least skimming through the list of new abstracts each
day.
- The NASA
Astrophysics
Data System (ADS). This is a web index of the
entire published astronomical literature. You can
search on
author name, title or abstract content, or object names and
ADS will
generate a list of publications that match your query,
including links
to electronically published articles or scanned versions of
journal
articles from the pre-electronic era. There are a lot
of nifty
things here, like the ability to search for papers that were
most often
also read by people who read a given paper.
- The NASA/IPAC
Extragalactic Database (NED). A searchable index
of
extragalactic objects including galaxies, quasars, galaxy
clusters,
etc. Users can search by object name or
coordinates.
- The SIMBAD
database. A database of Galactic objects, useful for
finding the
properties of a particular star, or for selecting a list of
stars
matching known criteria.
- The MAST archive
at the
Space Telescope Science Institute. This is an
multi-mission data
archive that includes the Hubble Space Telescope and many
other NASA
missions.
- The Sloan Digital Sky
Survey.
Users can search for objects matching a list of criteria
using SQL
queries and download images and spectra.
- The HEASARC
archive. A data archive of X-ray missions.
- Astronomy
Picture
of the Day. A nice resource for pretty pictures,
and
a good place to submit a picture from your own research if
you have
something you want to show off to the public.
- American Astronomical
Society.
Links to membership information, meetings, grants, and more.
- Astronomical
Society of
the Pacific. Links to membership information,
publications,
and an online store of astronomical stuff.
- International
Astronomy
Meetings List. A list of upcoming conferences.
- The AAS
Job Register. An online listing of job offerings
in
astronomy, updated monthly.
Observatory links: