Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5245c Report Date: 09-May-96:20:28 Version: ********** Check-in Date: ********** 1.Proposal Title: IMAGING THE HOT STELLAR CONTENT OF EARLY TYPE GALAXIES AS PART OF THE FOC/48 CAMPAIGN ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO 3728 Sub Category STELLAR POPULATIONS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Prof. Francesco Bertola UNIVERSITY OF PADOVA ITALY 39-49-8293436 PROF. OF ASTROPHYS. ------------------------------------------------------------------------------------ 7. Abstract WE PROPOSE TO IMAGE WITH THE FOC IN THE F/48 CONFIGURATION FIVE EARLY TYPE GALAXIES IN FOUR PASSBANDS CENTERED AT 1500 A, 2200 A, 2800 A AND 3400 A. WHEN COUPLED WITH PHOTOMETRY OBTAINED FROM THE GROUND OUR OBSERVATIONS WILL ALLOW US TO DERIVE COMPLETE SED OF THESE GALAXIES AS A FUNCTION OF THE DISTANCE FROM THE CENTER. THIS IS A KEY STEP TOWARDS THE UNDERSTANDING OF STELLAR POPULATIONS - IN PARTICULAR THE ONE RESPONSIBLE FOR THE UV EMISSION - IN EARLY TYPE GALAXIES AND WILL PROVIDE IMPORTANT INSIGHT IN THEIR FORMATION AND EVOLUTION. WE PLAN TO OBSERVE NGC 1399, NGC 2681, NGC 4552, NGC 5018 AND NGC 4627 WHICH SAMPLE A WIDE RANGE OF INTRINSIC PROPERTIES AS INDICATED BY PREVIOUS IUE OBSERVATIONS. FOR NGC 4627 THERE IS EVIDENCE OF ONGOING STAR FORMATION AND THE HST WILL BE ABLE TO SHOW THE CHARACTERISTIC CLUMPINESS. NGC 2681 HAD A STARBUST OF AGE GREATER THAN 1 GYR. NGC 4552 IS ONE OF THE MOST METAL RICH GALAXY KNOWN. NGC 1399 HAS THE SAME METALLICITY AND LUMINOSITY OF THE PREVIOUS GALAXY BUT IS A MUCH STRONGER X-RAY EMITTER. NGC 5018 IS A VERY GOOD CANDIDATE FOR ONGOING STAR FORMATION. WE BELIEVE IN THIS WAY WE CAN OBTAIN SED FOR THE TWO-DIMENSIONAL IMAGES OF EARLY TYPE GALAXIES FROM BROAD BAND IMAGING ALONE. THE CALIBRATION OF OUR FILTER SYSTEM WILL ALLOW US TO APPLY IT TO THE BIDIMENSIONAL ANALYSIS OF THE GENERAL SAMPLE OF EARLY TYPE GALAXIES. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 7.52 par: 0 10. Num targs pri: 5 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5245c PI: Prof. Francesco Bertola Proposal Title: IMAGING THE HOT STELLAR CONTENT OF EARLY TYPE GALAXIES AS PART OF THE FOC/48 CAMPAIGN ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Prof. Francesco Bertola DEPARTMENT OF ASTRONOMY PADOVA ITALY X Dr. Paola Amico DEPARTMENT OF ASTRONOMY PADOVA ITALY X Prof. David Burstein ARIZONA STATE UNIVERSITY U.S.A. Prof. Sperello Di Serego Alighie OSSERVATORIO ASTROFISICO DI ITALY X ARCETRI Dr. Laura Greggio DEPARTMENT OF ASTRONOMY BOLOGNA ITALY X Prof. Alvio Renzini DEPARTMENT OF ASTRONOMY BOLOGNA ITALY X ------------------------------------------------------------------------------------ 3. Description of proposed observations. We plan to obtain four images for each of the five galaxies in four passbands centered at 1500 A, 2200 A, 2800 A and 3400 A in order to measure the main features of the UV spectral energy distribution (SED). These data, once calibrated and joined with analogous measurements at longer wavelengths made from the ground should provide the radial trend in the spectral energy distribution longward of 1200 A with an accuracy of 10%. In order to obtain this goal we need to reach a S/N of at least 20 in the measurement of the smoothly distributed luminosity within concentric rings centred on the nucleus with thickness of 0.5 arcsec going from the nucleus up to a distance of about 7 arcsec, close to the edge of the F/48 field of view. If the UV radiation is concentrated in clumps instead of being smoothly distributed (expected if the hot stars are young), these will be easier to detect. We estimate that we should be able to detect with S/N=5 an upper main sequence O5V star at the distance of our objects in about 20 minutes in the F/48 + F150W + F130LP configuration. We have used the UV fluxes measured within the IUE large aperture (e.g. Burstein et al. 1988) and the assumption that the radial profiles in the UV are similar to those in the optical B and V bands to estimate the expected count rate and S/N ratio in each ring. For example for NGC 1399 in F/48 + F150W + F130LP we expect a count rate R_S = 4 cnt/s from the ring with thickness of 0.5 arcsec and mean radius of 7 arcsec (about 11000 pixel area). Since the background in this configuration is dominated by the detector dark counts (1.9E-3 cnt/s/px) the formula (1) on page 79 of the FOC Instrument Handbook (Version 2.0) shows that S/N=20 is reached in about 20 minutes. Rings at smaller radii all have higher S/N. Since our objects are all very red we have also evaluated the amount of red leak present in our UV exposures using the IUE spectra and the FOC total throughput curves obtained from the ST-ECF instrument database. The result is that about half of the radiation recorded in the F/48 + F150W + F130LP configuration is actually emitted at wavelengths above 2000A. The red leaks in the other filter configurations are considerably smaller. It is clear that the true spectral energy distribution will have to be spectrally deconvolved using our multiwavelength measurements and the FOC throughput curves. We can also use the IUE spectra to rescale the spectral energy distribution on an aperture equivalent to the IUE one. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. We need the unique imaging capability of HST in the ultraviolet, since this is the wavelength range where hot stars emit most of their radiation and are not ovewhelmed by the normal cold stars present in very large numbers in early- type galaxies. We also exploit the high spatial resolution of HST - still provided by the sharp core of the aberrated point spread function (PSF) - to search for the clumpiness in the spatial distribution of the UV radiation expected if the hot stars are young. We should be able to detect individually the massive young stars which might be present in our objects, thanks to the sharp core of the HST PSF and to the good discrimination against red stars in the UV. The IUE satellite, which we have used extensively to study the UV spectral energy distribution in early-type galaxies, cannot provide the detailed spatial information which is necessary to understand the nature of the hot stars present in these objects. In order to complement the HST observations it is planned to use the ground base telescopes at LA Silla and Steward Observatories to which members of our team have regular access. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. No special requests ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. We plan to use the data from the pipeline calibration (RDPS) at STScI. Eventual recalibration is possible using IRAF/STSDAS and the instrument database (CDBS). Analysis of the data will be carried out within MIDAS and/or IRAF, available both in Padova and in Firenze. An important step in the reduction procedure will be the elimination of the effects of the filter red leak and the recalibration using IUE spectra. Members of our team will upgrade our algorithms and reduction procedures so as to deal with any unespected technical condition. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. The PI (F.B.) and A.R. are Co-Is in a scientifically related CYCLE 2 proposal (PI R. Windhorst) concerning the UV spectroscopy of moderate to high redshift RADIOGALAXIES. A. R. is PI of a scientifically related Cycle 2 proposal seeking to determine the evolution with redshift of the main characteristics of the UV rising branch of ellipticals. D.B. is P.I of two related Cycle 2 proposals. One is to study the spectral energy distribution of extragalactic globular clusters and the nuclei of galaxies, including one of the galaxies proposed here (N1399). The other is to obtain mid-UV FOS spectra of AFG dwarf stars that can also be used as components of stellar population models. There is a clear complementarity among the five proposals. We have endeavored to construct these programs to make maximum use of HST resources. The scientific output of each of them would be enhanced by the successful completion of the other projects. Page 4 ------------------------------------------------------------------------------------ 9. Description of previous HST work. P2791:PAGB STARS IN ELLIPTICAL AND BULGE DOMINATED NEARBY GALAXIES (P.I. F. Bertola) The GO cycle 1 program received 8.45 hours of spacecraft time, with HIGH priority. It is related to this project. P2579: THE CALIBRATION OF THE WHITE DWARF DISTANCE SCALE FOR GLOBULAR CLUSTERS. (PI A. Renzini) The GO cycle 1 program received 45.80 hours of spacecraft time, with SUPPLEMENTAL priority. The program then completed the Phase 2, and was cleared for the HST observations. Subsequent to the spherical aberration problem the PI asked to DEFER the program to the first HST cycle with fully recovered WF/PC capabilities. The project 2579 is not closely related to the present proposal. P2570: RECENT MASS EJECTION FROM PLANETARY NEBULA NUCLEI.(PI H. BOND) The GO cycle 1 program received 3.73 hours of spacecraft time, with HIGH priority. The program then completed the Phase 2, and was cleared for the HST observations, which are now are scheduled for the summer/fall 1991. The project is not related to the present proposal. P2298: STELLAR POPULATIONS OF GLOBULAR CLUSTERS AND GALAXIES (P.I. D. BURSTEIN) The GO Cycle 1 program received 15 hr. HIGH PRIORITY time. It is related to the present proposal. Up to now only the image of NGC 205 has been delivered and we are in the process of deriving the luminosity function of the stars in the field. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Padova:VAX 8550 + MIDAS reduction package and SUN Sparcstation 2 Mod. GX + 1.5Gb disk + IRAF reduction package. ASU: DEC 5000-200 + DEC 3100 workstations, 2.6 Gbyte of disk; associated I/O devices; in a net with other workstations; access to Cray 4XMP. IRAF runs on both computers. ------------------------------------------------------------------------------------ 11. Address Information Name: FRANCESCO BERTOLA Category: PI Institution: DEPARTMENT OF ASTRONOMY Address: VICOLO OSSERVATORIO 5 City: PADOVA State: Zip Code: I-35122 Country: ITALY Telephone: 39-49-8293436 Telex (or e-mail): 432071 ASTROS I ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5245c [ 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 NGC1399 E,303 RA = 03H 38M 29.09S +/- J2000 V = 1380 1 SURF(B) = 20.6 +/- 0.2 0.1S, 2 F(1500) = 11 +/- 2 E-15 DEC = -35D 27' 03.5" +/- 1", 3 F(2200) = 4.6 +/- 2 E-15 PLATE-ID = 02IX 4 F(2750) = 7.6 +/- 2 E-15 5 F(3400) = 36 +/- 5 E-15 Comments: THE DATA IN FLUX REFERENCE NUMBERS 2 THROU 5 ARE FOR THE IUE LARGE SCIENCE APERTURE, EQUIVALENT TO A CIRCLE OF 7.5 ARCSEC RADIUS. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5245c [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1.1 NGC1399 FOC/48 IMAGE 512X102 F150W 1 25M 20 2 1 SAME ORIENT FOR 4 1.2-1.4 AS 1.1 CYCLE 2 / 1.1-1.4 ------------------------------------------------------------------------------------------------------------------------------------ 1.2 NGC1399 FOC/48 IMAGE 512X102 F220W 1 17M 20 3 1 4 ------------------------------------------------------------------------------------------------------------------------------------ 1.3 NGC1399 FOC/48 IMAGE 512X102 F275W 1 10M 20 4 1 4 ------------------------------------------------------------------------------------------------------------------------------------ 1.4 NGC1399 FOC/48 IMAGE 512X102 F342W 1 7M 20 5 1 4 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5245c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/48 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 7.52 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SAME ORIENT FOR 1.2-1.4 AS 1.1; CYCLE 2 / 1.1-1.4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F150W F220W F275W F342W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1399 ------------------------------------------------------------------------------------------------------------------------------------