Galactic Evolution: Importance of ubvy Standard Photometry
Workshop Completed [Back]
Posted by Peter Linde and Arde Ardeberg on July 06, 1999 at 10:26:50:
From: Peter Linde
Message-Id: <199907051957.VAA16716@nastol.astro.lu.se>
Subject: Comments on WF3 uvby filters
To: lupie@stsci.edu
Date: Mon, 5 Jul 1999 21:57:20 +0200 (METDST)
Dear Olivia Lupie,
Here follows our comments on necessary filters for the WF3:
What types of science do you envision doing with the WFC3?
Answer: With the HST, its WFPC2 and uvby photometry, we have just
successfully completed a study of star formation history and chemical
evolution based on (Me/H) and age data for individual stars in the dense
core of the LMC Bar. Down to V=22, we obtain (Me/H) data for
individual stars with an accuracy of better than 0.2 dex. Differential
age data are accurate to better than 25 %. Together, these data permit
tracing of galactic evolution of the LMC Bar over the latest 10 billion
years. We feel that for our understanding of galactic evolution such
data are badly needed for a reasonable sample of galaxies.
We envision a continuation of our studies of galactic evolution in other
galaxies in the vicinity of the Galaxy. Given a reasonable sensitivity
of the detector of the WFC3 (around 90 %), we can, without problems,
reach a number of such galaxies with the HST, the WFC3 and uvby
photometry. Suitable candidate galaxies are, with the corresponding
limiting magnitudes for (Me/H) to an accuracy of 0.2 dex
Sculptor, V=23
Draco, V=23
Ursa Minor, V=23
Fornax, V=22
Leo II, V=21
Leo I, V=20.5
We note that studies as proposed can be made both for field stars in
structural parts of galaxies with well-defined populations and in
globular clusters in the same galaxies, all the time with individual
stars as targets.
Of the filters currently on the straw man list .... ?
Answer: The uvby filters. This is a unique set of filters for
determination of high quality metallicities for individual stars. Data
from uvby photometry provide high accuracy (Me/H) data and ages for
individual stars much fainter than possible with spectroscopy of a
resolution necessary for corresponding accuracy. From wide band
photometry, no really reliable data on (Me/H) can be obtained.
Are there filters that are essential .... ?
We need the uvby filters, and they are on the list. Having the freedom
to wish, we would like to propose u and y filters closer to the standard
uvby system definition than at present available.
Given your expertise in the field, do you .... ?
We are quite satisfied with the list presently proposed, at the same
time as we like to refer to our answer to the previous question.
Best regards,
Peter Linde Arde Ardeberg
----------------------------------------------------------------------------
Peter Linde Tel: +46-46-222 4701
Lund Observatory E-mail: peter@astro.lu.se (Internet)
Box 43 Fax: +46-46-222 4614
S-221 00 Lund WWW: http://www.astro.lu.se
Sweden
Follow Ups: