Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4683c Report Date: 09-May-96:19:46 Version: ********** Check-in Date: ********** 1.Proposal Title: EVOLUTION OF GALAXIES IN INTERMEDIATE REDSHIFT CLUSTERS : IMAGING OF ABELL 665- CYC3 SUPPLEMENTAL ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO Sub Category EVOLUTION/COSMOLOGY ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Marijn Franx KAPTEYN ASTRONOMICAL INSTITU NETHERLAND ------------------------------------------------------------------------------------ 7. Abstract One of the more fundamental problems in current astronomy is that of galaxy evolution. We still do not have good constraints on how galaxy densities, types, and luminosities evolve with redshift. Most studies until now have used only photometric and spectrophotometric information to derive 'spectral' classifications and luminosities. Whereas these methods will remain essential to understanding evolution, they are insufficient for a unique interpretation of the data. I have started a ground-based program to measure dynamical parameters of galaxies in intermediate redshift clusters. I have successfully measured velocity dispersions, and in some cases, rotational velocities. These dynamical data are a fundamental step forward towards quantifying the effects of 'passive evolution', mergers, starburst, etc. For a proper interpretation, morphological information on the studied galaxies is necessary. I propose HST observations of the well-studied cluster A 665 at z=0.18 to obtain the necessary morphological information. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 2.20 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4683c PI: Marijn Franx Proposal Title: EVOLUTION OF GALAXIES IN INTERMEDIATE REDSHIFT CLUSTERS : IMAGING OF ABELL 665- CYC3 SUPPLEMENTAL ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Marijn Franx KAPTEYN ASTRONOMICAL INSTITUTE NETHERLANDS ------------------------------------------------------------------------------------ 3. Description of proposed observations. I propose to take WFPC images of Abell 665, a well studied cluster at a redshift of 0.18. This cluster is one of the clusters for which the Sunyaev-Zel'dovitch effect has been established$^1$, and a good dataset of spectra and radial velocities are available$^{2,3}$. I have already measured internal velocity dispersions for a sample of galaxies, and I will extend this sample in the near future. The HST images will allow a good morphological classification of the studied galaxies, essential before they can be used for the analysis. Although it would be of great interest to have very detailed information on the galaxies, it is clearly beyond the means of the current instruments to go beyond a classification of the galaxies; thus images will be taken in only one passband. Because of the large area that needs to be surveyed it is optimal to use the WF, despite the slightly performance due to the large pixel scale. Imaging with the PC would be too time consuming. It will be necessary to observe two separate fields to cover all the galaxies of the ground based program. \bigskip\parindent=0pt $^1$ Birkinshaw, Hughes and Arnaud, 1991, Ap. J. in press.\par $^2$ Oegerle, Fitchett, Hill, Hintzen, 1991, preprint.\par $^3$ Birkinshaw, private communication.\par ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The need for HST images is obvious if there were no spherical aberration: it would provide us with 2D photometry comparable to the ground-based data that can be achieved on Coma. Thus detailed structural studies would be possible. The spherical aberration reduces the quality of the data, but still allows for a good morphological classification of the galaxies, which is the main purpose of the current proposal. It is expected that fine structure caused by spiral arms, and mergers, can be recognized easily. It will be especially interesting to see if there is any evidence for a merger in the image of the large, post-starburst galaxy shown in Figure 1b of the scientific justification. There is no other such galaxy to date for which this type of kinematic data exists, and thus the HST images would be particularly useful. The power of the current HST for morphological studies has been demonstrated in a recent analysis by King \etal$^{1}$: These authors showed that several deconvolution techniques can produce useful images out to a surface brightnesses at which the Signal to Noise ratio is 10. They showed specifically how images with moderate integration times enable classification at low-intermediate redshift (around 0.2). Thus the proposed project is one of the types that HST still can do well, and are impossible to do from the ground. The reason is that the core of the PSF of HST (which is very narrow, but has not much energy) still provides the qualitative information on the galaxy structure. This information is completely absent in ground-based work. It will be harder to derive accurate quantitative information on these galaxies, as these will depend on the quality of the PSF. Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. As imaging in only one color is requested, I have chosen the passband which will produce the highest expected S/N. This is the ``R'' filter F702W. It has almost twice the throughput of other filters in the V to I wavelengths, mainly because of its width. A typical surface brightness for an elliptical at an effective radius is between 20.6 and 22.2 in R (K corrected). A 2000 sec exposure is expected to give a S/N of about 13 at a surface brightness of 22.2 mag/arcsec$^2$. Two exposures will be needed to verify the reality of the observed structures. These images will go deep enough to detect structures in disk galaxies to 1-2 effective radii. The integration times are optimal in the sense that the sky-photon noise will be comparable to the readout noise. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. The data analysis consists of 2 parts: the deconvolution for the morphological classification and the measurement of global photometric paramters. 1 Deconvolution : Recent tests on field galaxies have shown that the flux- conserving CLEAN method devised by Keel provides good results$^{1,2}$. This method can reconstruct the galaxy images as long as the S/N is higher than 10. The CLEAN algorithm works so well because of the strong peak in the PSF. Other techniques have been shown to give similar results. For the morphological classification it is not necessary to go beyond this step: the deconvolved images should be sufficient to type the galaxies. 2 Global Parameters : The global parameters like effective radius, surface brightness, and bulge to disk ratio will be derived directly from the data, i.e. bypassing the deconvolution. This can be achieved by minimization of the residuals of the convolved model with the data. The advantage of this method is that it allows for a much better determination of the errors (error estimates for deconvolved images are very complicated). The fitting procedure is very similar to procedures to determine velocity dispersions for galaxies: THe problem is transformed into Fourier space (a minimization in real space is the same as a minimization in Fourier space). Now the convolution with the PSF is a simple multiplication. The model parameters can be determined by a non-linear least-squares fit. The correlation matrix gives directly the errors and correlations of the fit. 1. King et al, 1991, AJ 102, 1553.\par 2. Keel 1988, ApJ 329, 532. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Any additional comments go here. ------------------------------------------------------------------------------------ 9. Description of previous HST work. A description of any previous HST data goes here. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). I am a full professor at the Kapteyn Institute, at the University of Groningen. The institute has provided me with a powerful workstation, and is able to fund students and postdocs for this research. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: MARIJN FRANX Category: PI Institution: Address: KAPTEYN ASTRONOMICAL INSTITUTE UNIVERSITY OF GRONINGEN P.O. BOX 800 City: GRONINGEN State: Zip Code: 9700 AV Country: NETHERLANDS Telephone: 011 31 50 634067 Telex (or e-mail): 53572 STARS NL ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4683c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL0665- F,404 RA= 08H26M09.77S +/-0.1S, 1950 Z= 0.18 1 SURF-BKG(R) = 19 +/- 1.0 POS1 DEC= +66D00'31.2" +/- 0.1", Comments: THIS POSITION IS REALLY ACCU- RATE. B1950 COORDINATES. WHEN CENTERED ON THIS POSI- TION, BRIGHT STAR IN SOUTHERN FIELD, WHICH WILL SATURATE CCD. OTHER BRIGHT STARS FORCE CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL0665- F,404 RA= 08H26M29.85S +/-0.1S, 1950 Z= 0.18 1 SURF-BKG(R) = 19 +/- 1.0 POS2 DEC= +66D00'11.1" +/- 0.1", Comments: THIS POSITION IS REALLY ACCU- RATE. B1950 COORDINATES. THIS FIELD DOES NOT CONTAIN BRIGHT STAR(S). ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4683c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE ABELL0665- WFC IMAGE WFALL- F702W CR-SPLIT=0.0 1400S 20 1 2 POS TARG +10,-10 ABE POS2 FIX CR- CYCLE 3 TOLERANCE=0.0 PRE-FLASH=YES PURGE=YES Comments: ORIENTATIONS 96 +-6, 186 +- 6 AND 276 +- 10 ARE ALSO ALLOWED. THIS IS THE LOWER PRIORITY EXPOSURE. WHEN BOTH FIELDS PLANNED CONSECUTIVELY, DO THIS FIELD FIRST. ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE ABELL0665- WFC IMAGE WFALL- F702W CR-SPLIT=0.0 1 1400S 20 1 1 POS TARG +10,-10 ABE POS1 FIX CR- CYCLE 3 TOLERANCE=0.0 PRE-FLASH=YES CLOCKS=YES Comments: ORIENTATIONS 96 +-10, 186 +- 10 AND 276 +- 10 ARE ALSO ALLOWED. THIS IS THE MOST IMPORTANT EXPOSURE. DO NOT USE WFC WITHIN ONE HOUR AFTER THIS EXPOSURE. WHEN BOTH FIELDS PLANNED CONSECUTIVELY, DO FIELD 2 FIRST. ------------------------------------------------------------------------------------------------------------------------------------ 3 USE ABE 3 CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4683c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=0.0 CR-TOLERANCE=0.0 PRE-FLASH=YES PURGE=YES CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 2.20 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category EVOLUTION/COSMOLOGY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG +10,-10 ; CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F702W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ABELL0665-POS1 ABELL0665-POS2 ------------------------------------------------------------------------------------------------------------------------------------