S T A N / W F P C 2 - Number 6, May 1995

CONTENTS:

• CYCLE 6 CALL FOR PROPOSALS
• WFPC2 NEWS
• WFPC2 Calibration Plan for Cycle 5
• Aperture and Wavelength Calibration for Linear Ramp Filters
• A Demonstration Script for Performing Aperture Photometry
• QUESTIONS, COMMENTS, ARTICLES
• THE HUBBLE DEEP FIELD
• SCIENCE WITH THE HUBBLE SPACE TELESCOPE - II
• DIGITAL SKY SURVEY ON-LINE
• RECENT PREPRINTS
• APPENDIX: WFPC2 Contacts

CYCLE 6 CALL FOR PROPOSALS

The cycle 6 call for proposals will be issued in early June. The proposal deadline for full electronic or paper plus electronic submissions is September 15, 1995. The results of the TAC deliberations will be distributed at the end of December.

If you did not received a copy of the Phase I Cycle 6 Documentation, you can request paper copies at hst_query@stsci.edu. PostScript versions of the Instrument Handbooks and all other documentation will be available on STEIS shortly.

WFPC2 NEWS

WFPC2 CALIBRATION PLAN FOR CYCLE 5

by Stefano Casertano

New programs have been designed to strengthen the WFPC2 calibration in areas where an improvement was deemed appropriate. This includes: observations of more standards, in both field and clusters, to refine the photometric zero points and the transformations to standard filters; fine measurements of WFPC2 sensitivity in the UV using crossed filters; detailed characterization of the PSF via substepped observations of a rich field; assessment of the dependence of CTE on image and background signal; recalibration of flat fields and throughput in ramps and polarizers; and an end-to-end check of the flat field quality on a stellar field.

The Calibration Program is described in detail in the WFPC2 Cycle 6 handbook which will be available on June 1. Individual calibration proposals will also be made available via Mosaic; the URL will be announced in future STAN issues.

APERTURE AND WAVELENGTH CALIBRATION FOR LINEAR RAMP FILTERS

by J. Biretta and C. Ritchie

WFPC2 contains four "linear ramp filters" which provide a narrow band imaging capability (bandpass FWHM ~ 1.5% of central wavelength) at most wavelengths in the range 3710 to 9762 Angstroms. These filters, known as FR418N, FR533N, FR680N, and FR868N, are essentially narrow band filters whose central wavelength varies as a function of position on the filter. To use these filters, observers merely specify filter and aperture names "LRF" and the desired central wavelength in their proposals. However, actual scheduling of these observations by STScI requires an accurate mapping from desired wavelength to target placement in the WFPC2 field of view.

Calibration of this mapping has now been completed. The results are based largely on pre-flight JPL tests, which give the run of wavelength on the individual filters, and on March 1995 on-orbit observations where flat fields were taken through linear ramp filters crossed with narrow band filters, so as to define the registration of the filters within the WFPC2 field of view.

The final products are two sets of mappings from wavelength to position in the field of view. The first mapping uses only the -33, -18, and 0 degree rotations of the filters, and contains ten small gaps in wavelength coverage. This "interim" mapping will be used until approximately. July 1995, when modifications will be completed to the spacecraft command system to allow a +15 degree filter rotation. At that time, there will be a switch-over to the "final" mapping, which allows observation at all wavelengths from 3710 to 9762 Angstroms (i.e. without gaps in the wavelength coverage).

For both mappings the unvignetted field of view is only ~10 arcseconds, and observers should be aware of this limitation when planning observations. All four CCDs (including the PC) are used at various wavelengths. We also note that a few small ranges in wavelength are observed effectively offset from the center of the filter passband; these wavelengths would otherwise fall off the CCD edges and be unobservable. The primary impact of these offsets is a slight loss in throughput (up to about 10% loss) at the affected wavelengths. The final wavelength mapping is described in version 3.0 of the WFPC2 Handbook, and a forthcoming Instrument Science Report will describe this calibration in detail.

Cycle 4 science proposals using the linear ramp filters are currently being processed and scheduled using the "interim" wavelength mapping table. We anticipate that Cycle 5 linear ramp proposals will be processed and scheduled without any delays. In the future, on-orbit photometric calibration of the ramps will take place during Cycle 5. We also plan on-orbit monitoring of the wavelength calibration to test for filter aging effects.

A DEMONSTRATION SCRIPT FOR PERFORMING APERTURE PHOTOMETRY

by Brad Whitmore and Inge Heyer

A demonstration IRAF/STSDAS script to perform aperture photometry on WFPC2 images of Omega-Cen has been developed. The primary goal is to provide an easy-to-use example to introduce observers to scripts and to demonstrate a few of the commonly used IRAF/STSDAS tasks. This script will also be used by the WFPC2 group at STScI as a template from which to test a wide variety of different effects on aperture photometry (e.g., hot pixels, CTE, undersampling, geometric distortions, edge effects, etc.).

QUESTIONS, COMMENTS, ARTICLES

We would like this newsletter to be a forum for interaction between users of the WFPC2. We'll be delighted to include articles and notes about WFPC2 data reduction and analysis. If, on the other hand, you have questions that would like to be asked to a wide (but "targeted") audience, you can send them, too.

THE HUBBLE DEEP FIELD

by Harry Ferguson (ferguson@stsci.edu)

During the next year, roughly 150 orbits of Hubble Space Telescope Director's Discretionary time will be the devoted to observations of a single area of sky. The purpose of this article is to advise interested astronomers of the status of the project and solicit comments from the community.

On March 31, a special Institute Advisory Committee met to discuss how to best utilize Cycle 5 Director's Discretionary time to make an impact on studies of the formation and evolution of galaxies. While there was a wide variety of opinions expressed, the committee finally recommended that the time be devoted to deep images of one field, making use of the Continuous Viewing Zone to increase the total exposure time. The imaging will be done as a community service, with no proprietary data rights so that the data would quickly be made available to the community for study and ground-based follow-up.

For the past several weeks an Institute working group has met to consider the field selection and observing strategy. The selection criteria are as follows.

• The field must be optimally placed in the Northern Continuous Viewing Zone (CVZ). This fixes the declination to be near +62 deg. The northern hemisphere was chosen to allow for follow up observations from the VLA, Keck, and KPNO observatories, although the desirability of selecting a second field in the southern CVZ is acknowledged, should this be possible in the future.
• It must be several degrees away from any bright star (>2 deg from stars <2 mag).
• It should be devoid of bright nearby galaxies, stars, known nearby clusters, and bright radio sources.
• It must have low extinction, low N_H, and low IRAS cirrus flux.

Three fields that meet these criteria are listed below. All are optimally visible at the end of December 1995.

ID   R.A.  (2000) Dec           l       b    E(B-V)   HI (x10**20 cm-2)
---------------------------------------------------------
HDF1 12 36 49.42  +62 13 46.3  125.885 54.82 0.0000  1.72
HDF2 12 28 37.89  +62 37 57.9  127.420 54.30 0.0000  1.54
HDF3 12 31 15.39  +62 12 42.3  127.006 54.76 0.0000  1.72

Field HDF1 is currently our prime field. The other two will be backups in case the first one has unsuitable guide stars, or sources too bright to allow deep radio imaging at the VLA (to be established in June), or other problems that come to our attention. We plan to take single-orbit test exposures of the fields in June (mostly to ensure that the guide stars are good). In the meantime, we are receptive to comments on the field selection, or, better still, images of the fields at any wavelength.

There is a reasonable amount of time before the HDF campaign starts in December to consider detailed strategies for filter selection and for parallel observations. We will provide updates in the future, and in the meantime are open to suggestions.

Please fell free to contact any of the members of the HDF Working Group:

       Mark Dickinson          med@stsci.edu
       Harry Ferguson          ferguson@stsci.edu
       Andy Fruchter           fruchter@stsci.edu
       Ron Gilliland           gillil@stsci.edu
       Mauro Giavalisco        giavalisco@stsci.edu
       Ray Lucas               lucas@stsci.edu
       Doug McElroy            mcelroy@stsci.edu
       Marc Postman            postman@stsci.edu
       Bob Williams            wms@stsci.edu

SCIENCE WITH THE HUBBLE SPACE TELESCOPE - II

by Ethan Schreier and F. Duccio Macchetto

A Scientific Conference co-organized by the ST ScI and ST-ECF
     Paris  (UNESCO Buildings)  December 4-8, 1995

During the two years following the Maintenance & Refurbishment Mission which restored the full capabilities of HST, this orbiting Observatory has produced very impressive scientific results, many of which have opened new insights into our understanding of the Universe.

The aim of this Conference is to present and discuss these results in all areas of astronomy. It will consist mainly of invited reviews. A limited number of contributed papers and posters will be possible. The program will include reviews of future HST Instruments, plans for future maintenance missions, and a Special Session on "Education and HST."

The Scientific Organizing Committee consists of P. Benvenuti, J. Bergeron, R. Fosbury, H. Hammel, R. Kirshner, R. Kudritzki, D. Macchetto, G. Miley, V. Rubin, and E. Schreier.

A Second Announcement, including a Registration Form and hotel information, will be distributed in June. The deadline for submission of titles and abstracts for contributed papers and posters will be in September 1995.

Please return the information below to Britt Sjošberg at the ST-ECF (bsjoeber@eso.org).

	Science with the Hubble Space Telescope - II


O       I intend to participate in the Conference
O       I intend to submit a Paper/Poster  
		Preliminary Title:
O       Please include my name in the distribution list

DIGITAL SKY SURVEY ON-LINE

The Digital Sky Survey, consisting of the 1950/55 Palomar Observatory Sky Survey red plates for the northern sky and the SERC Southern Sky Survey (including the SERC J Equatorial Extension and some short V-band plates at low galactic latitude) is available on line via the WWW at http://stdatu.stsci.edu/dss/dss_form.html or using StarView by clicking in the "Digitized Sky Survey" button in the Welcome screen.

A name resolver is available to find the coordinates of the object of interest.

Extractions can be saved in the following image formats:

   FITS 
   Standard FITS integer format (16 bits per pixel, 2 axes)

   FITS Unix-compressed
   FITS, compressed with Unix compress

   FITS gzip-compressed 
   FITS, compressed with gzip

   FITS with generic binary mime type 
   FITS, delivered with a MIME type of application/x-fits-binary. 
   Your browser should simply save this format to disk.

   GIF 
   The retrieved FITS scan will be converted to GIF.

If you are using a graphical Web browser (Mosaic, Netscape, etc), you may be able to configure your browser to display the FITS images returned by this form instead of saving them to disk. You can set your browser to recognize these FITS files and start SAOimage to take a quick look of the field. The StarView implementation includes a new version of SAOImage in which the cursor positions are given in RA and dec.

This service is intended to occasional, non-time critical users and small fields. Depending on the load and the size of the field, the access and response time could be very large.

Further information can be found in the help files (the "Strategy" button in StarView, for example). For comments, suggestions or if you experience any problems please contact archive@stsci.edu.

RECENT PREPRINTS

We draw your attention to these papers, based on WF/PC and WFPC2 data, that will appear in the next few months. This list includes all preprints received by the STScI Library not yet published in the journals. Please remember to include our Library in your preprint distribution list.

Bahcall, J.N.; Kirhakos, S.; Schneider, D.P.  
"PKS 2349-014: a luminous quasar with thin wisps, a large 
off-center nebulosity, and a close companion galaxy" 
ApJ accepted.

Bianchi, L.; Ford, H.; Bohlin, R.; Paresce, F.; De MARCHI, G.  
"HST imaging of the planetary nebula K648 in M15"  A&A 
accepted.

De Marchi, G.; Paresce, F. "Low mass stars in globular clusters. 
II. The mass function of M 15"  A&A accepted.

De Marchi, G.; Paresce, F.  
"Low mass stars in globular clusters. III. The mass function 
of 47 Tucanae"  A&A accepted.

Holtzman, J.A.; Burrows, C.J.; Casertano, S.; Hester, J.J.; 
Trauger, J.T.; Watson, A.M.; Worthey, G. "The photometric
performance and calibration of WFPC2"; PASP submitted.

Hunter, D.A.; Thronson, H.A. JR. "The massive stars of IZw18 
as seen in HST images"  ApJ accepted.

Shields, G.A.; Dufour, R.J.; Skillman, E.D.; Wyatt, R.J.
"The star formation history and chemical evolution of GR 8 
from HST observations".

APPENDIX: WFPC2 Contacts

Any questions about the scheduling of your observations should be addressed to your PRESTO contact. If you do not know who this person is, PRESTO's Mosaic page (http://presto.stsci.edu/public/propinfo.html) contains that information.

Post-Observation questions should be addressed to the WFPC2 Team, or analysis@stsci.edu.

Comments, questions, requests for issues, additions or deletions to the mailing list, etc. can be e-mailed to help@stsci.edu.

The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.