Lecture01: Where to Find Information
Lecture01: Where to Find Information
OUTLINE
- SIMBAD: Stellar Properties
- VizieR Catalog Service
- Aladin Interactive Sky Atlas
- Astrophysical Data Service (ADS)
- IDL: Excellent for plotting data
- Why write papers for the scientific journals
- Planning to write a scientific paper
- Techniques of writing a scientific paper
- Latex: An operating system independent language for manuscript preparation
- Problems for the student
SIMBAD: STELLAR PROPERTIES
- Smithsonian website
SIMBAD (2,800,000 astronomical objects).
- Strasbourg mirror website
SIMBAD
- Tutorials
- Query by object name (e.g., capella), catalog number (e.g., hd34029),
coordinates (RA and Dec, e.g., 05 16 41 +49 51 52), lists or parameters.
- Coordinates are specified by epoch and equinox. Specification of epoch
(if different from 2000) extrapolates proper motions from year 2000.
Specification of equinox (if different from 2000) implements precession of the
equinoxes from year 2000 (the large effect). The equinoxes precess with a
25,800 year period. This can be done in line 2d.
- Coordinates in RA and DEC. Also Galactic longitude and latitude and, if you
specify in line 2d, ecliptic coordinates.
(This is a good place for coordinate transformations).
- Proper motion in RA (mas/yr) and Dec (mas/yr). (mas=milliarcsecond)
- Radial velocity (km/s) and parallax (mas).
Distance = 1000 pc/parallax(mas).
- Many alternative names. Click on alternative name to get reference catalog
where the star was listed based on an observing criteria (e.g., instrument
used to observe it).
- Can make lists of types of objects in groups. For example, to get a list of
the 10 brightest B stars in the cluster NGC 2632 (Praesepe) type in line 1
Cl* NGC 2632 B and specify 10 in line 1a. To get the brightest T Tauri stars in
NGC 6611 type Cl* NGC 6611 T. Go to the "Dictionary of
Nomenclature" for more information.
- Aladin previewer of the star field around the specified coordinates using
data from different telescopes and satellites.
Read the Aladin
Sky Atlas Tutorial.
- One can display references to studies of the star (fetch the abstracts
and the full papers) and the measurements (best value given first).
- Go to the external archives and fetch the data.
- Can query the SIMBAD data base to get all objects meeting specified
criteria (Query by parameter)(A very useful way to create observing lists):
- Coordinates and search area.
- Constrained coodinates, parallax, radial velocity, magnitudes,
spectral types, etc.
- Presence in specified catalogs.
- Existence of specified measurements.
- Existence of stars in identified catalogs.
VIZIER CATALOG SERVICE
- Useful for finding stars and data in catalogs (5159 available on line).
- Website for VizieR
- Can find observations of a specified object in specified catalogs.
- Can get a list of catalogs that meet a specified criterion (e.g.,
ultraviolet) or mission or keyword.
- Can get data listings for the star requested (e.g., capella) from all
catalogs meeting a criterion (e.g., ultraviolet). (For some reason HST was
not included).
- Click on a specified observation in the listing for a given catalog to
get the metadata and to a browse spectrum or the data.
- To browse catalogs directly go to
Astronomer's Bazaar
- When all else fails and you cannot locate a website, try
Google
ALADIN INTERACTIVE SKY ATLAS
- Website for Aladin
Interactive Sky Atlas
- Visualize digitized images of any part of the sky and superimpose entries
from any catalog or personalized data files.
- Very useful for visualizing multispectral band images. One can
superimpose images from different catalogs using different color to identify
different spectral bands.
- Read the documentation before you get too deep into Aladin.
ASTROPHYSICAL DATA SERVICE (ADS)
- Webstite at CfA ADS
- Strasbourg mirror site ADS
- Excellent for locating published papers in the refereed and nonrefereed
literature.
- Astronomy and Astrophysics literature and ArXiV preprints
(primarily astro-ph).
- Can search by author and/or words in title and/abstract.
- A new and very powerful tool is to seach the full text of all 2.5M papers
in the ADS data base for a given word or a string of words.
- Simplify the output by specifying date intervals to be searched and use
filters (i.e., only refereed papers).
- When you click on a reference, you can read abstract and download
the full paper.
- Also One can get a list of all papers that have cited the paper in
question (to see later papers on the same topic).
- Also can list the "also-read articles" on the same topic or "find
"similar abstracts".
- To download figures and tables from papers choose the "electronic
version" option and click on the small version of a figure.
Then save the file and play with it.
INTERACTIVE DATA LANGUAGE (IDL)
- IDL is a proprietary language for plotting data and data visualization.
- The Department has a site license and there are manuals in many places.
- If you make the effort, you can become a very sophisticated IDL
programmer who can produce for publication true works of art.
- First write an IDL procedure (e.g., simpleplot.pro), then start IDL by
typing IDL, Then start your procedure by typing .run simpleplot.pro
- For the sample proceedure, the output plot of the data is idl.ps
- You are free to download my sample IDL procedure
and modify it to plot what you wish.
- This procedure plots dh vs dfe with both variables having error bars
(from dhp to dhm and from dfep to dfem) and a weighted least-squares linear
fit to the data with the axes labelled.
- You can find many special purpose fitting and statistical routines
in the IDL manuals or write your own. A good source is "Numerical Recipes" by
Press et al.
WHY WRITE PAPERS FOR THE SCIENTIC JOURNALS
- Publishing papers in the scientific literature (journals and books)
and oral presentations at scientific meetings and seminars) are the only
way of telling the rest of the world what you have done and making yourself
known.
- Great ideas, excellent observing and data analysis skills, and hard work
are not sufficieint. Your collegues need to know what you have done.
- So developing writing skills and lecture skills are critically important.
(ASTROPHYSICS IS A LITERARY PROFESSION.) Developing good writing skills
and organizing how you write will help prevent "writer's block".
- English in the lingua franca of contemporary science just as
Latin, French, and German used to be and perhaps Chinese will be.
- Creativity and the ability to bring together insights, data, and theory
from different fields of research is important in creating an excellent
paper.
PLANNING TO WRITE A SCIENTIFIC PAPER
- You need a new idea or a way to take an existing idea forward. This
involves either a new dataset with which to address a problem, a new or
more developed theoretical approach, or a way of combining or reanalyzing
existing data sets from the archives.
- Acquire the data you need either from new observations or from data
archives.
- Find from the literature or (better) develop yourself a model for
understanding the data.
- Work closely with collaborators who can provide the data, models, or
understanding of what has been done in the past. Don't be afraid to ask
for help (even from somebody who you do not know.)
TECHNIQUES FOR WRITING A SCIENTIFIC PAPER
- Use first person (singular if you are the sole author) active voice. ("I
observed the star." not "The star was observed.")
- Develop a logical approach including the following steps:
- Clearly state the problem to be solved.
- Describe the previous work (observational and theoretical) and say why
this work should and can be improved.
- Describe the new data (which instruments, which modes, when, S/N,
where archived, etc.).
- Describe the data reduction and analysis proceedure.
- Develop or cite the theoretical approach used to make the model used to
understand the data.
- Discuss the implications of your work and what new obserations of theory
are needed to carry this work forward.
- Summarize your work and its conclusions.
- Consider writing the paper in the following order:
- Data figures (Plot measured quantities against time, space, and other
quantities to show functional or statistical relations. Include predictions
of various theories or models in the figures for comparison with the data).
- A "cartoon" that shows how your model works and how it explains the data.
(Bengt Gustafsson is the expert for this.)
- Title (Summarize your conclusions in a few words. This can be a real
challenge so be creative.)
- Abstract (Say what you have done and why it is important in the grand
scheme of astrophysics all in one paragraph).
- Tables of data or model predictions.
- Text that says what you have already shown in the figures, "cartoon",
title, abstract, and tables. (At this point the text is easy since you have
already done most of the work.)
- References and acknowledgements.
- Start with a macro that is either a test manuscript file from the journal
website or a file of another paper written for the same journal.
Then keep all of the formatting material and replace all of the content.
- Write the paper in a language that is independent of computer operating
systems so that you can iterate back and forth among the coauthors without
having to remove the "signatures" of different operating systems. This
language must be able to include figures, equations, tables, etc.
LATEX: AN OPERATING SYSTEM INDEPENDENT LANGUAGE FOR MANUSCRIPT PREPARATION
- Two good manuals are: A Guide to LATEX 2e by H. Kopka and
P.W. Daly, and LATEX User's Guide and Reference Manual by L. Lamport.
- Advantages of using LATEX:
- All lines of LATEX code are pure ascii so all machines can read it.
There are no unique symbols or encryption. LATEX is nonproprietary and
therefore is independent of operating system.
- LATEX can easily include figures (.ps, .eps, .pdf) and can adjust the
size, location, and orientation of figures.
- LATEX can include complicated equations and Greek and other script
characters.
- Tables are easily included in portrait and landscape mode.
- Conversion from the .tex code to the page layout is done with a
nonproprietary translator code, but the "expert" can visualize the page
layout directly from the .tex code.
- Disadvantages of using LATEX:
- LATEX may not be in your PC. You will have to download it.
- You do not immediately see the page layout unless you are an expert.
- All commands are written into the .tex file rather than by clicking on
icons. So, you need to learn the basic commands. There is a learning curve.
- Running a LATEX file
- edit file.tex using your text editor
- latex file coverts file.tex into file.dvi
(a device-independent translated
file)
- dvips file will then print the page layout from file.dvi
- dvips -o file.ps file creates (but not print) the file.ps
(postscript)
file
- Where to get sample LATEX files and instructions for their use from
astronomical journals:
- Let's look at a sample file for a paper recently published in A+A
PROBLEMS FOR THE STUDENT
- Make a list of all O-type stars with B magnitudes between 2 and 4 which
can be observed from Boulder. Plot their locations in the sky in Galactic
and ecliptic coordinates. Is there a pattern in the data? TBD
- Make a list of all brown dwarfs described in the catalogs of infrared
observations. Plot their locations in Galactic coordinates. Which of these
stars have been detected at x-ray and ultraviolet wavelengths? TBD
- Make a list of the 10 highest proper motion stars that have b oth x-ray
and ultraviolet detections. Plot their x-ray vs ultraviolet fluxes.
TBD
- Make a list of the 10 brightest x-ray sources in the Ursa Major cluster
(Col 285).
Plot their location in ecliptic coordinates at epoch 0 and overplot their
location at epoch 2000. Has the big Dipper changed in shape in 2000 years?
TBD
- What is known about the Trapezium Cluster (NGC 1976) stars?
How many stars are in
the cluster? What are their properties? Plot the ratio of their x-ray/UV
fluxes vs B magnitude. TBD
- Make a list of the rotational velocities of all G stars located within
30 pc. Plot their rotational velocities vs their x-ray fluxes. Is their a
correlation? TBD
- Make a list of the 20 brightest O-type stars that are not known to be
binaries. Plot their x-ray vs bolometric luminosities (or fluxes). Is there a
correlation that is statistically significant? TBD
- Plot the 50 brightest members of the Hyades Cluster in Galactic
coordinates. Overplot (in different colors) their X-ray and infrared fluxes.
TBD
- The young star T Tauri (the prototype of the T Tauri class of stars)
is now known to be multiple. When was this
discovered and at what wavelength was this discovery made? TBD